Planning baby at 19?

I'm 19, about to be 20 in October. My boyfriend (23) and I have been together for 3 years, have our own 2 bedroom apartment, our own cars, we both work and pay our own bills, I have one year left of college and we are very happy and very stable. I know that ultimately it is our own decision, and it is something we both really want. I didn't get much time with my mom and I want as many years I can get with my children. But sometimes I hear my friends, who are all young mothers, say they wish they waited or that they feel trapped. I just don't want to feel that way while I have to choice because once we conceive there's no going back! Does anyone regret planning their babies young? Or have any advice to offer?