Is webcam sex bad for a 17 year old?

I'm turning 17 really soon.I've always appear to be nice and innocent, good at schoolwork...but secretly I have sexual thoughts which haunt me.So I did webcam sex with a guy.It felt good when I was doing it, but afterwards I feel dirty inside.I can't believe what I did last night.I'm going crazy! What should I　ｄｏ？