Yes, it could be - have you had your kidneys checked for an infection - or have you been involved in something that may have caused them to crack - sport, sneezing too hard, being hit? Go and get it checked out would be my advice.
no idea but you should go see a doc. like right now.
It sounds to me like your back is out of alignment. A trip to a chiropractor will probably fix you right up.
If u had sex and the guy was on top could make your ribs hurt I dated a guy once use to make my ribs kill me hope u feel better