Pain on left side

I'm 20.5 weeks pregnant, and I've had a pain on my left side since Sunday evening. It's sharp at times, other times I don't feel it unless I turn that way. I had a strong feeling it was gas, and I am still skeptical, however I've never had it last for days. My doctor was barely able to squeeze me in later today, but do any of you know what it could possibly be? I'm a first time mom. And just to add, I feel like I've still felt my baby moving around in there. I'm just worried! 

Thank you in advance!!