18 yrs old, and dating an 18 boy with 2 kids..stressful? yup.

Sometimes I ask myself why I am dating the guy I am dating. If anybody knew how stressful the situations I go through are, they would instantly break it off. But why do I continue to date him? When we were in high school, I always had a crush on him and we finally started dating our senior year. One slight problem. Our sophomore year, he got a girl pregnant and had a new baby girl born at the age of 15. Another problem, the same thing happened two fall seasons later.  He got yet another girl pregnant at the age of 17 and now has two baby girls. I don't think anybody realizes how difficult to handle the situations that arise and understands what its like to have to deal with the ex-girlfriends (baby mammas). Sometimes I am really okay with it, and I just look at is as a package deal. But other parts of me are really not okay with it. He really does not take much responsibility in caring for the girls, which at my age seems "right" even though I know it is more than wrong for him not to spend time with his children. I am not sure exactly what to do, now that the kiddos are almost 3 years old and almost 1. We are both head over heels in love, and I have been dealing with this problem for almost a year and a few months now. Is the love and the happiness I get when we are together worth the stress of him already having two children? I don't know. I will never know. We did split up, and a few short months later we could not take being apart anymore. I know we are in love. He means the world to me, but I know I can do better. It is a really difficult situation, but I just learned to take it and deal with it. Is there anyone else who is 18 and is in a situation like this? I need advice from another girl in this same situation. Thank you.