Ladies who've miscarried before.

I miscarried last August, I'm pregnant again-12 weeks. I've seen my baby twice-both times baby has had a heartbeat. I'm still throwing up so that's a good sign, but I'm convinced something isn't right! I don't have a reason too though-anyone experience this before, I'm assuming I'm just scared because I've miscarried before. But man I just can't let it go!