I need to change my lifestyle. I'm unhappy & need support!

Sounds like a plan to me!! I would just make sure that you dont take it too heavy too fast. By this I mean dont over work your body. It can be easy to get super excited about something like this and then over do it on the first day. Pace yourself with the excercise and listen to your body (thats not to say dont push yourself) Good Luck :-)

Good luck on your journey!!! I feel like I need to urge you to change your "lifestyle" to something sustainable - what I mean is, are you going to be able to live the rest of your life on absolutely no junk food or drinking nothing other than water? You may be able to lose the weight, but I would hate to see you set yourself up for failure!!! What may make it easier for you is to watch your calorie intake - you are allowed to have those "junkier" foods, as long as they fit into your calorie goals. Good luck!

1200 cals are way too low for you. This is my daily intake (136lbs) + exercise calories which I sometimes eat, sometimes not. If you are on 1200 and plan to be reasonably full you have to make almost 100 % healthy choices - whole grain with surplus of lean proteins and daily recommended portions of fruit, vegetable, diary BUT no sugar, no cookies, no chocolate, no junk food, no calories in drink, no alcohol, no salty greasy snacks. Can you do it?
As of exercise I have a plan to do 5-6 exercises a week. Sometimes it's impossible to squeeze workout into my schedule but I don't bother about it. I will do tommorow extra 15 minutes of weight training or cardio. Both planning my meals and working out are growing into habits.

One step at a time and you can be on top of Mount Everest...

I think making so many changes all at once, along with not taking rest days and eating a low amount of calories is setting yourself up to fail and feel worse about yourself.

Check out the sexy pants link. http://www.myfitnesspal.com/topics/show/1175494-a-guide-to-get-you-started-on-your-path-to-sexypants?hl=guide+to+sexy+pants&page=1#posts-18362157

What does it matter if you do it in 100 days or 200 or 300 or 500 or 600 if it means what you do lasts a lifetime?

I think making so many changes all at once, along with not taking rest days and eating a low amount of calories is setting yourself up to fail and feel worse about yourself.

Check out the sexy pants link. http://www.myfitnesspal.com/topics/show/1175494-a-guide-to-get-you-started-on-your-path-to-sexypants?hl=guide+to+sexy+pants&page=1#posts-18362157

What does it matter if you do it in 100 days or 200 or 300 or 500 or 600 if it means what you do lasts a lifetime?

^This

I'm 19 years old, I weigh 215 lbs and I'm disgusted. I've never been this big before. I don't look huge, but I feel sluggish and awful as well looking it.
I have decided to work out for 100 days straight starting tomorrow (Feb. 7th, 2014). My end date will be May 17th 2014.

My ultimate goal is to lose about 50 for the result of 165 lbs.

Daily calorie intake: 1200

During this 100 day challenge, I plan on making healthier food choices (no junk food, more fruits and vegetables as well as only drinking water and occasional black coffee) and exercising every day. I will be doing jumping jacks, running, pushups, squats, wall sits, along with some lifting.

Will this help reduce fat and cellulite?

I'm hoping for some major progress by the end of the 100 days, as well as feeling better about myself (mentally and physically).

What do you all think? Good idea?

Terrible idea, too much exercise, too few calories, too much weight too fast. This plan is just setting you up for failure.

Instead, workout 3-5 days a week (your body needs recovery time) Lift heavy and do some cardio. Figure out your TDEE based on that level of activity and reduce your intake by 20%. Get healthy, cut slowly, this isn't a race, it's a journey.

Rigger

I am not expecting to lose 50 lbs in 100 days by any means! I just want to shed the excess!

But what excess are you talking about?

Most people around here who have dropped weight and kept it off for a long period of time are going to tell you the same thing --- don't do anything that isn't sustainable for a lifetime. Eat the most you can while still dropping weight. Choose exercise you enjoy (or at hate the least).

Why is this first 100 days any different than the rest of your life? Having goals great, but having too many or goals that are too restrictive means you are likely to spread your energy too thin.

Read the link we've posted.

I'm 19 years old, I weigh 215 lbs and I'm disgusted. I've never been this big before. I don't look huge, but I feel sluggish and awful as well looking it.
I have decided to work out for 100 days straight starting tomorrow (Feb. 7th, 2014). My end date will be May 17th 2014.

My ultimate goal is to lose about 50 for the result of 165 lbs.

Daily calorie intake: 1200

During this 100 day challenge, I plan on making healthier food choices (no junk food, more fruits and vegetables as well as only drinking water and occasional black coffee) and exercising every day. I will be doing jumping jacks, running, pushups, squats, wall sits, along with some lifting.

Will this help reduce fat and cellulite?

I'm hoping for some major progress by the end of the 100 days, as well as feeling better about myself (mentally and physically).

What do you all think? Good idea?

HI! I see some flaws in this plan haha. Don't over do it, wear yourself out. It's okay to be semi-healthy at the start and slowly become healthier.
First off though 1200 calories? Uh no no no. Don't do that to your body, love it haha don't starve it. I'm 5'7" and at 148 ate at aprox 1700 calories a day to lose half a pound a week. I dont know your height but find our your TDEE and subtract from there!
The healthier food choices is great and where I personally struggle, a great goal + plan to have!
Working out everyday is okay if its not the same muscle group. And if it's not too high intensity everyday. I'd make a plan, something along the lines of this.
Sunday
Strength Leg Day

Tuesday
High intensity cardio

Wednesday
Strength Arm Day

Thursday
Yoga/Pilates/Etc.

Friday
High Intensity Cardio

Saturday
Ab day.

Obviously thats just an example but you get the gist! (Or if you're more lazy like me you can only work out 3x a week )
It will help reduce fat.
Cellulite is not to be guaranteed at all. I know stick thin girls who have it. Just life.