Go back to hand lead dolphin. Do it with fins if necessary, but do it very slowly and let your chest and shoulders rise all the way up to the surface between pulses. If you rush it, you will be trying to take a stroke when you are still deep under water. When you have it right, it feels sort of like sliding over the top of a roller coaster. Just do as many as you can before needing a breath at first.
On that note - don't pulse down too deeply, let your neck stay relaxed so that your chin moves forward a bit on the downward pulses. Think of sliding your body forward through a narrow chute, rather than bobbing up and down.
Another thing to be aware of is your elbow position. You want to keep your elbows high when catching. But don't add the catch in until you have come up to the surface on the hand lead dolphins.