chances of a miscarriage after just having one?

I had a miscarriage at 7 weeks about 2 months ago and it was truly such an awful experience. In all honesty though, I’m sure I was the reason I miscarried. I was drinking and smoking even after finding out. I know it was a horrible and sickening thing to do and I would really appreciate if no one gave me hate because I entirely regret what I’ve done. After thinking about it long and hard I realized I would change my ways tried to get pregnant again and now I’m 5 weeks. I’ve committed to not smoking/drinking. I really want this baby. But, for some reason.. I feel like at any given moment I’ll just miscarry again and be disappointed. I’m stressed out lately, I haven’t been eating as healthy as I should... hormones got me crying tons, & I’m always moving in positions where my stomach gives me sharp pains. I’m really worried.. My first appt is next week but I’m just still so scared about miscarrying again. What are the chances it could happen?? & what are some things that could avoid it!!