The reason why I'm asking is because I was talking to my good friend heather and she said she thinks I'm depressed.
Also I have friends who told me " Since you got in a relationship you seem so happy " And I asked what do you mean like I wasn't happy before, and all of my friends said the same thing " Well, its just you always seem so upset "
Teachers have asked me SO MANY TIMES " Is everything okay? " and I'm like Yeah I'm fine, and they just say okay.

Anyway,
I will admit I have some problems...
1. I cry at least 2 times every week before bed
2. I cut myself open A couple times on my upper arms
3. I am trying to stop eating and lose weight
4. I KNOW I'm unhappy inside. I can feel it.
I cry because I feel alone and ugly and like nobody likes me, I feel like I have no one to talk to, because I tend to push them all away. I cut myself because I feel worthless and the pain just evens out from emotional and physical. It's sort of self obvious as to why I'm trying to lose weight. I feel FAT. I'm 12 and I weigh 100pounds and I am 5'1. Also I have the biggest thighs in the world.

BUT, then there are general times when I'm totally fine. But something is always on my mind, I always have a problem, and in school sometimes I just stop working because I get too stressed out or confused and just give up. I lose interest in things easily and just like being alone in my room for hours in the dark.
Even right now as I'm writing this at 10:18PM. I've been in my room since 1pm just in the dark with my door locked. I could sit in black and just be in deep thought for hours, but if I think too much I could cry.

So, Do you think I'm Depressed? And if I am, what should I do?

You may show some depression symptoms, but I don't think you would diagnosed with depression. Otherwise, you would be too "depressed" to even get on the computer and care enough to input such a thought/opinion. I do, however, think you are going through such a phase. A lot of teenagers go through it, and it's normal. Minus the cutting yourself part, that is SERIOUSLY dangerous, especially for a TWELVE year old. You are in no way a professional at cutting yourself nor do I suppose you understand where the "proper" place to cut yourself could be. If you happened to cut yourself any lower than where you are, you could easily strike a major vein, that is if you are cutting deep enough, and it is an easy way to bleed to death. Possibilities are small, but still is a risk that is irreversible. Also, like you said, you are twelve? This is a BIT early to be worrying about this stuff, normally anyway. But even if, the average weight for a twelve year old can vary from 90 pounds to 110 pounds depending on genetics and what not. Not to mention, you still have many many years to grow and develop. You have just barely began. Twelve, like I said, is still a bit young to worry. Also, if you, so to speak, have "the biggest thighs in the world" and still weigh 100 pounds, you would have to be extremely thin, so then I wouldn't see why you call yourself "fat". Honestly, I think you are too young to worry about self esteem issues. Trust me, if you don't take care of it now, then you will really be a wreck by the time you hit actual teenage hood. Just worry about being a kid! And if it would help, maybe talk to your parents? A school counselor? Hope this helps. Really, just be yourself and don't try to hurt your still developing body with starvation or cutting.

Best thing to do, considering your only 12 is chat to your parents? Or someone who you think you can trust and talk to freely. I'm nearly 16 now and I remember being your age and thinking that certain things like my weight and peoples opinions of me were the end of the world, but as you grow older you realise there are worse things that could happen, I'm not trying to patronise you as I hate when people do that but use this as reassurance. As for your weight, you are at a healthy weight for your height, so there is nothing to worry about! As for the self harming and being in your room for most of the day, try and find a hobby, something that you enjoy doing and do it! You'll also make friends, just be confident in what you do and always try to look on the bright side by not thinking about things so much. Im no doctor, so I couldn't tell you if you were depressed but just remember, a problem shared is a problem halved, so talk to someone in your family. X