Hi.
While there is no specific way that you should feel, maybe you should still be thankful for now that you aren't pregnant. Consider for a moment why you and your boyfriend would have wanted that. Your reasons may not be so similar. Talk about it and see how valid your reasons are. It may also help to talk to someone else about it.
If I seem to be taking this a tad seriously, it's because I am. You just got out of a bit of a bind and you're lucky. The fact that you took three pregnancy tests indicates that this is important to you. The question is why exactly is it important to you. I guess you've read the stories of many girls here and you've seen how much their pregnancies has changed their lives. Though very few or none of them would consider a life without their children, they would've had an easier more teenage life if they didn't get pregnant.
Consider your experience a pat on the behind by a loving father or mother who caught you fooling around, scared you a bit with a few well-placed words and set you off again with a firm but gentle pat on the behind.
Look, you're not supposed to be having all that sex yet. Not to seem prudish here but that is the truth. The reason why people ask you to keep sex within the confines of marriage is that aside from the moral issues, it really does keep things simple.
You can say now that you want a baby and your boyfriend can, too. Volunteer to help out in an orphanage for two straight weeks or more. Go there everyday. See how well you love kids. Kids seem to be okay when they're all cute and cuddly. They're not so cute when you're trying to study for an exam and you have your period.
Try to find posts here regarding women who're trying to finish college while taking care of a baby or posts regarding women who initially had supportive boyfriends who ended up being left alone. You may say that your boyfriend's different. Sadly, you only really get to know that at the end.
Please take care of yourself and try and beg off sex for now.
Erick