Help!!

My freshman year, I met the guy of my dreams. Turns out he's just another asshole in disguise. So. Here I am 3 years later and the piece of shit still has control over my heart.. I haven't slept with another guy since because he's been pulling on my heart strings ever since we broke up and if I even think about being in a relationship with another guy he makes me feel so guilty about it I back out to please him... I know it's not right but I do it... I've been told before that having sex with another person will help let him go, is that true or just some shit a guy told me because he wanted in my pants? I just need advice, how do I get over him... my first love..