Is it possible to train?

I guess I would say I have delayed ejaculation. I can make myself cum in 5-10 masturbating. But sex takes longer, and I cannot cum from a blowjob at all. One thing I’ve noticed is that years of masturbation has made it where I think I need to thrust in order to cum. So I think laying back and receiving a blowjob just doesn’t hit the same. My head isn’t as sensitive as other Peoples seem to be. Sex and blowjobs and everything still feel good. But I just feel that I am extreeeemely particular about cumming. Sometimes my girlfriend gets me close, and then I notice something silly like the fan is blowing hard, and all the sudden I’m not about to cum anymore. It can be very frustrating.

I have tried the OFM, but honestly I don’t think I could get myself to cum that way. My head isn’t particularly sensitive, is it ok to just do it on the shaft? Or should I still train the head?

Honestly I’d love to become a prejac. But any step in the right direction would be nice. Any help?