My hair needs help! Can somebody help (: please?

I'm 17 years old and where I live is mostly hot. My hair tends to dry out more when it's hot. My hair is very stressable. I always straighten it because that's the only way it looks good. But I think it's bad to just straighten my hair. When I get straight out the shower I let my hair dry and once it drys it's so curly and like a Afro ! I hate it ! Everytime I try to put mouse or hairspray it still gets big and nasty. I would like to stop straighting my hair for a while but do any of you guts know a cream or serum or something I can put in my hair once I get out the shower ? Something that will define my curls and help it stay? It would help alot! (: oh also my hair was thick but I've noticed it has been thinning and I don't like that at all ! &&'d my hair is falling out! I feel so sad because I really like my hair (when it's straighten ) and hopefully when I find something it will get better.