Did I screw up my metabolism?

My guess is you've been eating far more than 1300-1500 calories. A plateau just means you've been eating at maintenance so for a male of your weight maintenance level would be a lot higher than 1500 calories a day which s why I think you've been eating more than you think. I weight 186 pounds and I'm the same height and my maintenance is around 2400 calories. Without seeing your diary it's hard to look for any inaccuracies. I would suggest looking at the link below to sort out any inaccurate logging.

It is in fact pretty difficult to muck up your metabolism it normally takes years of disordered eating or a metabolic condition to do this. As for your calorie goal you should be eating more than 1500 calories (which I think you have been anyway) eating too low calories means you will lose far to much muscle mass which is a thing you really don't want to happen. Have a look at the links Good luck

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

http://www.myfitnesspal.com/topics/show/1175494-a-guide-to-get-you-started-on-your-path-to-sexypants?hl=guide+to+sexypants&page=1#posts-18361594

MFP tells me I should be eating around 2100 calories to loose weight. I started, and continue to eat around 1300-1500 calories with a lot of lean protein and it have been working great for me.

Why do you eat 1300-1500 if the daily amount is 2100?

ETA
And how do you measure your food?

I don't think that's enough calories for someone your size. I have had a plateau for the last 3.5 weeks and at the advice of members here I have raised my cals from 1300 to 1600. In the week since I've done so, I still haven't lost, but haven't gained either. I was told that due to the extreme addition in my workout program that I was indeed retaining water, and that accounts for the plateau.
I'm a 5"3.5 135 woman.

I will admit when it comes to actually measuring my food I guess mostly.

Yup.

How's that working out for you?

Until you weigh your food and track accurately, the numbers you put into myftinesspal are meaningless. Start again fresh. Weigh and track 100% of your food. Pick a reasonable level of calories to eat for someone your weight and height. Eat those calories every single day. Don't have a cheat day/meal. After a few weeks of accurately counting, if weight doesn't move, slowly remove calories. Anytime weight stalls, before lowering calories, ask yourself if you are tracking accurately and accounting for regular cheat meals.

Hard to believe, but it IS possible to eat TOO FEW calories, to wit, this article I found at the Everyday Health site:

If you're like most people who want to lose weight, you want to lose it fast. So you may be tempted to make drastic changes in your diet to dramatically reduce the number of calories you consume. But what you may not know is that eating too few calories can actually backfire and sabotage your weight-loss efforts.

"It would make sense to stop eating [when you are trying to lose weight], but it actually works in the opposite way," says Kimberly Lummus, MS, RD, Texas Dietetic Association media representative and public relations coordinator at the Austin Dietetic Association in Austin, Texas.

Calories and Your Health

The most effective way to lose weight is to consume fewer calories than you expend, creating a calorie deficit. But if your calorie intake dips too low, says Lummus, your body could go into starvation mode. "Your body will start to store fat because it thinks it is not going to get anything," says Lummus. "You will be at a point where your body is kind of at a standstill."

Lummus says that when your body goes into starvation mode, your metabolism slows to a crawl, burning calories as slowly as possible to conserve its energy stores. This is why people who cut their calories too much may reach a plateau and stop losing weight.

Back to me: so eat what the app tells you... from my experience, it's pretty accurate in its calculations, as long as you tell it the truth.

OP maybe try taking a diet break. spend a week or 2 eating at maintenance .

PS i dont weigh my food either, refuse to do so since i really dont want to be obsessing over food like that. BUT i also assume that i'm eating 200-400 more calories than i have logged.

I'm a 27yr old 5"10 female (174cm).... I weigh approx 180lb (81kg)... i work out most days... I do cardio and strength (as per my job requirements)... I eat 1800-2000 calories a day (some days 2200) and I have been losing consistently... I would starve on 1500-1600 as I need the calories for energy and recovery!

It is in fact pretty difficult to muck up your metabolism it normally takes years of disordered eating or a metabolic condition to do this. As for your calorie goal you should be eating more than 1500 calories (which I think you have been anyway) eating too low calories means you will lose far to much muscle mass which is a thing you really don't want to happen. Have a look at the links Good luck

How does 3 months sound to lower your total daily sedentary burn by 20% below what is expected, and by only taking a 25% deficit from a lab measured TDEE?

Years? Hardly.

And make it more than 25%, as OP did, and you can find the normal help resistance training can give won't be nearly as helpful.

http://www.myfitnesspal.com/blog/heybales/view/reduced-metabolism-tdee-beyond-expected-from-weight-loss-616251

http://www.youtube.com/watch?v=2i_cmltmQ6A

http://www.myfitnesspal.com/topics/show/1077746-starvation-mode-adaptive-thermogenesis-and-weight-loss

As to OP's issue - the above is possibility, so is poor food logging (though that would have to be just totally awful to overcome that much potential deficit), and 10 days not enough time for a real plateau.