This is by no means medical advice, but a few things:
1) Speak to a doctor. My ex had PC and that was the reason he went to a doctor. He had a few other symptoms he was ignoring, but sex being his whole life, that made him go to a doctor.
2) Try drinking more water.
3) Jackoff by yourself and take a long time with it. Edge as much as you can and see if you precum. For me, it depends on how turned on I am. If I'm just stroking off quickly, not much. If I even think about fucking my boyfriend, a river.