I cant stop giving every one the evil glare, even when im happy...halp?

Okay..id had this problem since i was small. I would stare off into space or be completly happy, not really angry at all but i still have the evil glare...when i actually try to smile or i am smilling, most of the time my smile come out as a expression of nothing... I had even tried smile in the mirror and my face still look nuteral. But than i gave a big fake smile...it ended up looking hella creepy. And thanx to this its hard for ppl to feel comfortable or even like being around meh. I want to know why is my facial expressions are hard to do while trying not to look all fake. It has even started problems W/some of the other girls in my class. They think i wana fight or something. Thats when i started hid my face W/my hair. That seemed to work but it gives my alot of blemishs. Can some1 plz tell meh if there is anyways to change this or if theres a name for this? Any kinda help would be nice. Thnx