OakleyRx8

Hello I'm new on here. Anyway I have a 04 rx8 and for some reason it's been making a loud squeaking noise only when I'm in 1st and 2nd gear it starts after my car has warmed up so when the temp gauge is in the middle. The squeak goes away when I put it in neutral one of my friends said it could be the serpentine belt but I just have no clue. It also squeaks when i turn, but once again its either in 1st or 2nd gear, Please help if you know what the problem is. Thank you very much.