I don't think it's the pill that is causing this because you said you have no problem getting "lubricated" when you're on your own. I would say that you need more foreplay - it sounds like you're trying to rush into things, sex shouldn't be rushed into take your time and the lubrication will come. If it was the pill it wouldn't make any sense that you'd be fine when you masturbate but not fine with your guy so I put it down to rushing things. Without going into too much detail, maybe try some new things with him?