Sorry to hear about the troubles man.... Also sorry to say, hey, it's part of life... Sure you hear about the high school sweethearts getting hitched and living happily ever after, but seriously, that isn't the norm.
You will learn to adapt to the feelings, and be able to handle it better.
I dunno who broke up with who, or why it happened, but let me tell you this.... I was with a girl for over 4 years. We lived together in an apartment, got pets, then bought a house. Not gonna go into real granular detail, because I don't care.... It's over, we are done. I caught her doing questionable things, and I picked up the phone the next day and told her mom (we were buds) that she had to come home, or find somewhere else to stay, cause I am totally done.
Months later, I went out with another girl who was too young (for me.... legal, but too young & imature for me...), and while I was with her, I still had strong feelings for my ex, so I broke up with the youngin. The ex and I hung out a few times, and EVERY time we would get into an arguement.... we both have come to realize and accept that we bring out the absolute WORST in eachother.
So I stayed single for a while more, and met the most perfect, gorgeous woman. We've been together since July, and things are great. I really have no complaints at all... We have similar family lives, both big into family, our families like eachother, and have actually known each other for MANY MANY years. Her older brother and I grew up together and were best buds.
At any rate man.... my suggestion is this: Carry on with your life. Don't dwell on the past. Don't let past relationships, or relationships at all determine what you do at this point. Go to a college because that is where you want to go, not because you think you'll be able to spend more time with your girl if you go there... You're 18, still an adolescent, and have lots more living to do before you should worry about relationships.... Trust me... I am preachin this, cause I took the other road, and made a HUGE mistake at the age of 20.... No, didn't have a kid, but not gonna go into details.