help...sports bra for nursing moms?

I'm 6 weeks pp and just started back to my workout routine. I'm also breastfeeding, and struggling a little with clogged ducts. I've already had mastitis once and am petrified to get it again. The first time I went back to the gym, I wore one of my normal sports bras which admittedly is probably too small now for my DDD's (normally just a D cup). After I got home I noticed some sensitivity and realized that compression may be a bad idea. But tonight I worked out again in a normal bra and my boobs were all over the place, and they hurt!!! Does anyone have any recommendations or experience with this? Is a larger compression sports bra the only option or is there something I'm missing??