Exhausted from sex

My Boyfriend and I TTC ... It's only been a few weeks and I'm exhausted ... Lol... I need advice I don't want to hurt his feelings but we been having sex up to 4x a night and before I go to work ...I am a nurse & I barely sleep... How can I speak to him without him getting upset? I spoke to him about ovulation times and he stated he don't believe in that... I would fall asleep and 10 minutes later he's starting again. I love that he is so committed and want this as much as I do. But, I want to enjoy our time and not make it feel like work..