I think that quite often there can be this immense pressure on guys to 'perform'. It is like we forget about enjoying the journey for its own sake and think that it is goal directed towards the guy ejaculating. If that happens then sex is a success, and if it doesn't then it is a failure.

Sometimes the way around the psychological road block can be to rediscover enjoyment in sexual activity without it being goal directed. Does he like watching you masterbate? Or would he enjoy stimulating you manually or orally or whatever?

Taking the pressure to perform off can make it a whole heap more enjoyable at any rate...