I think a guy likes me that i might like back yet my friend likes him :L :L?

It sounds to me like this guy is playing both sides of the fence. He knows that your friend likes him yet he is flirting with you and obviously hasn't mentioned to your friend that he doesn't like her in that way. This could cause some major problems with your friend especially as you mentioned she may have some self-esteem problems in this area (this may be, this may not be, but I'm uming it is since you brought up her weight in this situation). Watch out because you may gain a boyfriend and break the heart and trust of a friend, tread lightly.