I have been with my boyfriend for a few months now, and we generally have great sex. However, sometimes he has difficulty getting and or sustaining his erection. I have noticed that this is typically if we try to have sex two days in a row. It seems like if we have a break, there is no problem. We occasionally have morning sex after having sex the night before and sometimes that goes OK and others there is trouble. He does not seem to want to talk about it and says everything is fine (he'll usually say he's just tired or he doesn't know what's up with him), but it makes me nervous that there could be something I am doing wrong or not doing that would solve the problem. I get the sense that maybe he just has a lower sex drive than me, but maybe does not want to disappointing so he tries even when he's not really in the mood? Anyone else have similar issues or some advice? We are both in our mid 20s and I have never experienced any kind of sexual issues with a guy, so I am just out of my depth here. I don't want it to develop into anything worse and I am worried that he might start over thinking it if it happens too many more times.