Causes of pinching pain?

Sooo yesterday I started getting this pinching pain in my uterus. On the left side like right above where my pubes would be.
 It's not like it's unbearable or anything, just kinda uncomfortable. And it only lasted a couple hours, I also got it for a couple minutes today. Everything I looked up is steady saying "implantation" but I feel like it'd be way to soon for that, and according to this app I wasn't even fertile at the time a had sex. I don't even think I've been fertile this month, cause like my cm is white and creamy, but then again I'm new at all this 😅 any suggestions?