Thanks so much for all of your wisdom ladies! I took out both the bobbin and top thread and vacuumed the bobbin casing. It helped, but I still had bumps. I think the thread is thicker than what I've been using. I pulled out my other thread and used that instead.
This time I had a very few bumps, maybe 5 on 45 piecings. I realize I shouldn't have any. I'm going to look into the tension settings and see if that solves it.
Thanks again ladies!