I'm having pain in my left side below my ribs when I inhale or strech. It's been going in for 3 days.

Have you done anything strenuous lately? It sounds like a pulled muscle. But obviously if you are concerned about it, go see the doctor so you can know for sure.

Could also be a pinched nerve. Herniated disc. Slipped disc. Plus a dozen more off the top of my head. A doctor is the best bet. Could be simple, but could be not.