Why do I get cramps in my hip when I do sit ups?
If your a rookie it's normal your just strenghtening your muscles because they are not used to such exercises - they just work twice as more so u'll get used to it .
Maybe it means ur getting stronger
When I do sit ups the top of my butt hurts
you could be over working your muscles or that is a new muscle you haven't worked yet
Probably because ur kind of leaning to the side when doing it.
It's because of the lack of oxygen. Make sure you are taking deep breaths while working out. In your nose, out your mouth.