Sorta religious / Karma?

So I've had this sort of paranoia or superstition I guess. So im christian and I believe in God, but what I've worried is a tad confusing and let me know if you don't understand. So you know the saying what goes around comes around? Well I always had a worry that say you mistreat someone or you commit a sin, would God punish you while you're on Earth, say like make things go bad in your life not like anything severe but I mean little things here and there. I don't know how to explain it but for a while I've been self conscious and worried that if I did little sins here and there that God would make little things here and there go bad? Can someone like explain to me how thats is or isn't true, it bugs me all day every day.