Seeing black spots!

Elisabeth
I'm 33 weeks 5 days pregnant. A few weeks ago I was having little black floaties in my vision, but I figured it was due to overheating since I was outside in 100+ degree weather. The past couple of days though the spots have come back in my vision and I haven't been overheating or overworking myself. 
Any thoughts? I know sometimes black spots in your vision can be a sign of preeclampsia. My doctors haven't voiced any concerns about my blood pressure at my previous appointments.