seeing black spots? 31 weeks pregnant?

So for the past couple weeks occasionally i will see what looks like a bunch of little gnats flying around...but when i try to look directly at them there is nothing there...i just had a dr. Appt friday and i told her about them and she said she wasnt worried because my blood pressure was perfectly fine and has been throughout my entire pregnancy...is this normal? I dont have dizziness or headaches or anything...but when i see the spots its not just a few of them it always looks like a bunch of gnats....my eyes have also felt very heavy...like im extremely tired but im not...i dont know whats going on!

They're called "floaters". I Have had them my whole life, but they are a lot worse now that I am pregnant. Dr's are only concerned with them if you have high BP.