if it helps in any way, my girlfriend of 2 years, was 20 when she had her first boyfriend. He ended up cheating on her shortly after, and got with me some time later.
I also lived with a guy a while back, and he didn't have a girlfriend till he was 24-25. He and his girlfriend ended up getting engaged later that year.
I know how frustrating it is (I was often given the "your so sweet, but I love you like a brother" speech), and trust me when I say this, but sometimes, focusing so hard on something for too long can actually make achieving it harder!
I'm almost falling asleep right now (not long taken my meds), but I'll be back tomorrow to see what anyone else has said, and try and help you out
Take care dude, and try not too let it get you too upset (i know, much easier said than done).