What happens if my muscles ache while i'm at the gym should i stop?

Try staying with it: If you were able to keep up normally in gym class / sports as a kid, you probably do not have McArdle's or one of the other muscle diseases that make hard exercise impossible at your age. De-conditioned muscle will be damaged some when you work it hard, but this will pass. Do some good stretching beforehand, and try hitting the weights even harder; stop only if your urine turns dark brown.