Try a noise gate, which turns down the volume during pauses in speech, so it reduces breath noises. Noise gates are available in hardware or software. Some manufacturers are Drawmer and Alesis, among others.
To use a hardware noise gate,
1. Plug the mic into a mic preamp or small mixer that has phantom power.
2. Connect the output of the preamp or mixer to the noise gate input.
3. Connect the noise gate output to your sound card or audio interface line input.
4. While talking, adjust the gate threshold so that breathing during pauses is inaudible but speech is not gated or cut off.
To use a software (plug-in) noise gate in a recording program, insert it into the track that your speech is recorded on. While playing the track, adjust the gate threshold as described above.
Ideally you would use a headworn mic in which the mic capsule is to the side of the mouth to prevent breath pops. Crown no longer makes one, but you could make one by taping a Crown GLM-100 mini mic ($185) to a bent coathanger wire that goes around your head and over both ears, with a "boom" extending from one ear to the side of your mouth. Good luck!