trouble sleeping

soooo....I don't have a bed. Just a full bed frame and a twin size air mattress where the bed should be...sometimes I sleep on the couch. But sleeping on the air mattress really sucks because if it's not too hard then it's too soft and I get really weird cold sweats...don't know what that's all about. I NEED TO FIND A FULL SIZE MATTRESS AND BOX SPRING FOR CHEAP!!!!! UGH!! If you can help that'd be AWESOME!