Sara,
My weakness in any stroke has always been the kick. Here is a breaststroke kicking drill that works for me.
With a kickboard, of course, push off the wall and glide trying to keep your feet stretched out straight with your big toes touching. as you slow down, draw your legs up as if you were trying to kick yourself in your backside. When you have drawn them up as far as possible, turn your toes out as far as possible and snap them back to the stretched out position with your big toes touching or almost touching. Pretend you are drawing half circles or ellipses with your heels.Straight line up to your backside, an ellipse back to where your big toes touch and stretch. Remember to try to keep it fluid. You only stop when you are stretched out or as they call it, "I position". Glide for a three count , kick again. I think you'll surprise yourself how well your kick will get when you just focus on it with no pull with arms. I'm sure there are tons of coaches out there that can explain this better than me, but that was my best effort to describe something that has worked for me when I was a serious swimmer. (early 1980's) .I still do this exercise almost weekly. I kick 2-300yds. then swim 100yds. 1 length sprint,1 length stretch. I mix it in my normal workout actually when I'm out of breath and need to rest a bit. I'm sorry to ramble on and I hope this helps you a little.
Tony
OMG, my 100th post and I didn't get to tell a joke... I know, how can I convince you that this drill only works while in the nude and being filmed for freediving on youtube video?? So take my advice if you will, but please share the video with us, we would love to critique your technique.