Why does ever girl I like, not like me back?

Ok, every girl I like/have liked in the last 5 or so years hasnt like me back… Several have hated me simply for m likeing them, and then theres the 2 that I actually fell in love with… And no, this isnt just childish love, this is more like “I bought you a ring, wrote 2 pages of poetry, pour out my heart, changed just about everything I can about me, and bent to your wiill” kinda love.

Ok so both these girls dont like me. One went out with me for 2 years but never let me even touch her, the other one wont even go out with me.

Im 180cm tall, dark brown hair, near perfect teeth, dark brown/black eyes (changes with mood) and reasonable build, yet still very slim. Male, btw. The one that did go out with me is still one of my best friends, even though we have our little fights and arguments… But then can be expected when she starts screwing your best friend, right?

Anyways, it isnt that I aim to high, or have high standards… These girls are just average, normal looking girls. Nothing fancy, no huge tits, no model bodies, no extra glam. Just normal girls. And it isnt that im horrible looking, im tall and rather well built… Infact, im a 28- hour a week sportsman,. So it isnt me being fat or anything.

And a lot of the girls who only just meet me think im really good looking, take for example girls I meet at school disco’s or my friends friend (many of which whom I never meet again) anyway can someone explain to me why its only ever the girls I like who dont like me back? Because a lot of girls who do like me are either my sisters friends, my best-friends ex’s, or too young. So its not that im being picky with them… Anyways, does anyone else get this?