Why so many gnats in my house?

I have spent the day running around my house killing gnats randomly. Lately there has been an unusual amount flying around. So I was taking a piss and i noticed a lot on the shower curtain so after I finished i went and checked the tub and there were at least 50 maybe even more gnats just sitting in the tub, I immediately freaked out and got my mom stating that there was "an unnatural amount of gnats". My whole family is baffeled and we are freaking out at how gross this is... WHY ARE THEY ALL IN HERE? help?!