Unless it's a serious heart murmur, like a grade 3 or higher, it's unlikely to affect you very much. I was born with one. It's never stopped me from doing anything. My doctor checks it once a year at my annual physical and that's about it. It is more noticeable if I'm carrying a few extra pounds. (noticeable to my doc. I still don't really notice much.)

Good luck. Hope it turns out to be minor.