Mine does the same, although it's more of a weekly change, some weeks I feel like I could more than happily just stay in bed and have sex on a loop! Other weeks, I'm not that fussed. Being a woman though I think that's to do with all the hormonal ups and downs we go through in a month

! Not sure - do guys have hormonal cycles too??! You have to remember too that when you were 16, pretty much all you had to worry about in life was homework, and whether or not you could manage to sneak in past your curfew. At 24 you're having to start worrying about the more grown up stuff in life - and stress will definitely have an effect on it. Hope that helps!