Happy but scared!!

I finally got pregnant after trying for so long, now I'm scared that something bad is gonna happen as I have a history of miscarriages and one time without a heart beat while still pregnant. My fiancé lost his 5 yr old daughter years ago and I don't want to put him through anything like that again. I keep thinking that I might be bleeding or the cramping I feel is me losing the baby. I know this stress is no good, any advice to keep me healthy so I don't have to worry?