from 1500 calories to 2500 calories

You didn't lose on 1500, but now on 2500 you do? That sounds a bit strange ..

Hi there. Good job on making a commitment to yourself. I noticed that we are friends; hi friend! I'm a big guy too at 6'4''. When I started MFP last year I was at 270 lbs, so we may be comparable in our starting stats. I wanted to address your question. First, 1500 calories is far too little food for you to eat. Yes, it's not dangerous for you, but that kind of deficit is hard t maintain for men of our stature. I started my weight loss at 1600-1700 for the first couple months and like you lost a 20 pounds in the first month. Aftera couple months I began to feel light-headed and weak. No matter now I tweaked my macros or meal times I was hitting a wall. Upping my calories to around 1900-2000 saw the light-headedness subside. When my BMI dropped to around 25, though, found that I needed to eat a little more than that with my job that keeps me on my feet all day. I do suspect that I had more readily accessible fat stores to burn when I was heavier. I am only conjecturing because I'm not an expert and also I know that the more fat we carry around the more calories we require to support body function and also the very fat stores we carry around.

You will notice that after your initial weight loss (the 14 pounds) you will only be losing 1-2.5 lbs a week. This is because at 2000-2500 calories a day, you are eating at a 5000-8000 calorie a week deficit -- the equivalent of those 1.2.5 lbs. This is just where you should be. Remember that as you lose weight your calorie requirements will go down though. That 2500 calories will turn into 2100 -- it did for me!

Good luck.

Remember that this takes a long time. Losing weight is simple. The hard part is preventing or managing the cravings and resultant binging. The body is sneaky and will -- seemingly out of the blue -- decide to make you hungrier than normal even if nothing has appeared to change in your habits or lifestyle. Those moments are crucial. Eat a little more if it keeps you in control. If you're anything like me you can reverse two months' worth of good, clean living with a week of binging. If that happens, I need to find the courage within me or through something drastic and external -- a wake-up call -- to right me on my path.

You didn't lose on 1500, but now on 2500 you do? That sounds a bit strange ..

Nop - normal - starving yourself does not necessarilly rhyme with losing weight (faster).

So before downloading myfitnesspal app I was eating very little maybe less than 1500 calories for
Maybe 2 or 3 weeks ..but before 2 weeks I started counting my calories and doing 2500 diet plan

For 1 week I didnt lose any weight and I was afraid I was going to gain becuase the big change from 1500 to 2500
the second week I have only lost 1/2 lb

I dont know should I continue doing this or eat more or less calories

I'm 294 lb 6.4 ft 23 years old

I'm not counting macros and not doing any cardio

It looks like 2500 net calories will have you losing 1 lb per week. Do you exercise, and are you eating back exercise calories as well? You've only done this a short amount of time and probably just need to be patient, weight does fluctuate normally. However with just a one pound deficit you may need to be a bit more precise with your food measurement, otherwise inadvertent under estimating of food calories could wipe out your deficit. Please read the links below for some tips you could consider incorporating:

http://www.myfitnesspal.com/topics/show/1296011-calorie-counting-101

http://www.myfitnesspal.com/topics/show/1234699-logging-accurately-step-by-step-guide

http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

Jumped from 1500 to 2500 in one day i assume?
Increase in calories needs to be slow and methodical - your body is used at 1500, throwing down nearly the double in one seating will not be of much use.

And why is this?

I'd say depends on how long he has been crashing calories.
Assumption is that a 294 lbs lad on a 1500 calories has probably a rather slow metabolism and a considerable amount of the weight loss is not fat burning based.
Jumping from 1500 to 2500 in 1 shot will not leave your weight loss journey on a linear basis (OP is the first person who admitted it) - weight loss froze and eventually slowed down.
Gradually increasing calories (realistically if you know what you are doing you would increase fat and carbs but leave protein at bay) will keep your weight loss going, gradually replenish glycogen / water and gradually ramp up your metabolism - body will shift from storing as much as possible into fat and eventually nourish muscle which will eventually counter effect fat storage.

Tried it - more than once - not with the same caloric amplitude and not in the same overall conditions.
This is actually the principle of reverse dieting (and one of it's uses).
Taking your calories up from big deficit and at times not so healthy eating pattern (with all it's side effects well in place) and bring you back to a healthy and steady eating pattern and maximizing results.

As another user has mentioned, temporary weight gain is nothing to be worried about, and the OP has only been doing this for 2-3 weeks. There's nothing to suggest a damaged metabolism. If you increased intake sharply and didn't lose weight after sufficient time had lapsed, then the food was increased past TDEE.

One thing I will agree though, if instead we increase gradually and check on progress every month or so, the results should be more reliable as far as finding that spot where you're losing at the expected pace. It could also help account for inaccuracies in food logging where OP might find that "2000" calories is the sweet spot for losing 1 lb per week, but when he digs deeper and logs accurately, that 2000 may really be more like 2500