Hey girl,
I was sixteen when I got pregnant for the first time, luckily, my boyfriend was supportive, and he stayed with me through it all and in June 2004, we had a beautiful baby boy, and I was seventeen at the time. After that, we found out that I was pregnant with another baby, and we had her in December 2005, and now, we are married, since May 13, 2006, and I just started my second trimester with our third child, this one is due in december too. So, an extra baby will put extra strain on your relationship, but it's worth it when your in love and you have your beautiful children together, so, don't worry about having another baby, it can work.
Good Luck,
Michellle J.