I need support?!?! Pregant with baby#4!

So here is my story..I am a mom I put up a baby for adoption to a family member when I was to young to keep her..so that's why I am only a mom currently to 2 boys..one is 5 years old and the other is 5 mos..Has anyone had a pre-term baby because of the close age? I am worried that I might not go full term! I never had a baby early they were all around 39-40 weeks except my last one was 40+5! There isn't a family history of per-term baby's and I never had one! But I know it can happen due to having him only 5 months old and expecting again..Blood work came back as high #'s which tells me its a good sign!! But has anyone else had a baby and gotten pregnant again?! And had their baby be fine and healthy!?