If you think about something as you drift to sleep, you will tend to influence the dreams you have that night. Choosing to dream about sex is usually a challenge because thinking about sex tends to lead to a level of arousal which makes it a challenge to actually get to sleep. It sounds like when you now think about sex it does not lead to that kind of obstacle. It wouldn't keep you awake. Maybe you would find that a dream about sex is better because it will tend to involve stronger emotions than during waking hours. Also the body will be more relaxed in sleep. This could improve your chances. If you do manage to have an orgasm during your dream the pleasure tends to carry over to waking hours. If there is just something temporary going on it could be a way around whatever the obstacle is and then it will be easier to enjoy sex while awake.