Needing help, so worried!

So I had my 5th kid at 31 weeks, have no idea why? I was just about to go to bed when I thought my water broke, it was actually blood and not my water! Rushed to hospital, I was dilated to 6cm...tries to give me mag but I wouldn't stop bleeding and they were worried about me losing so much blood so the y had me deliver. They checked my placenta but never found a reason for it. He's fine now and healthy! BUT, I just found out I'm pregnant again, and I'm soooo scared this will happen again!?! I did some research and found out that if you had one before it's more likely, also if you get pregnant before 18 mo after birth its high risk too. It's only been 4 mo since I had him. I'm terrified, anybody ever have two preemies in a row, or gotten pregnant back to back and carry full term?