Why can't I gain weight?

I'm 5'5"-5'6" and I weigh 95 pounds. No matter how much I eat, I can't gain weight. I hate my body. I think I look skeletal, not as bad as people with eating disorders (I don't have any of the negative side effects of being so thin- I get a regular period and I don't get dizzy, etc. I've been checked out by a doctor and there's no medical reason for me being so thin). Still I have had complete strangers tell me to eat more to my face and I always feel like people are staring at me. It really sucks because even though people tell me it's better than being obese I get more crap for it and people think it's okay. So my BMR is 1,400-1,500. I've been purposely counting my calories and consistently for the past two weeks I've always consumed at least 2,500 calories. Yesterday I ate about 3,200, which is the highest so far. I really don't think I could eat anymore; I already eat until I feel full and don't let myself ever get hungry throughout the day. Eating is starting to feel like a chore. Any tips?