I don't know what to do anymore...

I agree with MyOwnSunshine that counseling may help.
Beyond that, I would recommend increasing your exercise time if you can. Vary it so that you are challenging your body in new ways. If you can't afford a coach, go to a class, and if you can't afford a class, go to the library and borrow exercise videos or do videos on youtube.
Exercise to make your body ready for the fun you want to be having.
Schedule a time each day for moping. If you feel down and it's not your scheduled time to mope, say "I'll get to that later."

A talk with a professional is probably a really helpful idea :flowerforyou:

If you want to feel positive about yourself and truly start looking at food as fuel instead of a fat trap, look into strength training. Lift some heavy stuff. Put your heart and mind into it. When you start seeing the positive changes that are happening, you'll be hooked. You will need food to fuel your workouts and you'll be glad you ate healthily. Oh and all that lean muscle wont look half bad either

I would recommend increasing your exercise time if you can. Vary it so that you are challenging your body in new ways. If you can't afford a coach, go to a class, and if you can't afford a class, go to the library and borrow exercise videos or do videos on youtube.
Exercise to make your body ready for the fun you want to be having.
Schedule a time each day for moping. If you feel down and it's not your scheduled time to mope, say "I'll get to that later."

This is really bad advice. She's 112 pounds and sees herself as fat, which is obviously a skewed body image. I have a feeling she will not be happy with her body until she takes care of what's going on inside of her. I know, I've been there.

Also, what's this comment about moping? Her wording indicates a path down an eating disordered road, which I really would not classify as moping.

http://en.wikipedia.org/wiki/Body_dysmorphic_disorder

i agree with previous posters i would seek help.. i looked at your pic . i dont think your fat.. i think its something you need to heal on the inside before you can change your perception of yourself of what you look like on the outside

starving yourself is not the answer

seeking help proves your strong and you want to practice self care. do they have a guidance counselor in your school.

:flowerforyou:

But earlier I went to take a shower and I just lost it. I looked in the mirror and all I saw was fat. My belly. My love handles. My thighs. Everything. I hated my body. I felt gross and horrible.

I don't want to do anything. I don't want to eat or sleep. I don't want to go out with friends and family, or read and write. I don't want to watch TV. I'm not even sure if I want to live (I am NOT suicidal or even contemplating it). I just feel worthless and I have no one to talk to.

Honey, you need help. More help than some people on the internet can offer.
What you're listing are symptoms of depression & body dysmorphic disorder.
Go to your school's health service & ask about counsellors, or they should be able to refer you to free or low-cost community resources.

I was 140lbs at 5'4. I'm 19 and now 112ish

Going by BMI, both of those are within a healthy range, but barely.
http://www.shapeup.org/bmi/bmi6.pdf

I started excercising without eating back exercise calories

In order to lose weight, that's what you should do. That's what my doctor told me to do & it's working.
But since you're at the low end of a healthy weight range, you need to be eating them back now.

Recently, I've felt almost proud of myself. I didn't feel fat anymore.

But now I've lost that. ... I keep getting caught in a cycle of being happy, then hating myself. I can't get out of it. I fell again earlier.

Can your brain "get" that you shouldn't lose any more weight?
Can you understand that your current weight is in the healthy range, but only barely?
Ignore your feelings, go with facts here, because your feelings about yourself are screwed up.
Until you get them more in line with reality, rely on things that don't change - numbers are objective.

I looked at your profile picture of your tummy, and the worst I can say is that you're maybe a bit lacking in muscle tone.
Girls are supposed to be softly padded. You're doing it right.

If you want to be more toned, do regular weightlifting. Maybe that's what you need to like how you look. Your weight may not change, or may even increase slightly, but that's OK, you've got plenty of room above you in the healthy range.
While you can't spot-reduce fat, you can target the abdomen / trunk to get better toned. Work all the way around - situps, twists, side situps, back extensions, leg lifts.
Heck, throw in some hip exercises (abduction, adduction, kickbacks) and you'll be looking awesome from hip to bust.
Do the upper body too & you'll be amazing all over.

I'll post it in the comments once I figure out how.

Post it to photobucket (or a similar hosting page), then copy the URL & put it into your post like this:
[ img] http://URL.com [ /img]
but leave out the spaces in the [] area.