severe depression related to love life

I was talking to this guy for almost a year and he promised me that he was only talking to me. I found out that he was talking to other girls behind my back, and that ruined me. I've been crying nonstop and turned to self injury and over dosing my anxiety meds. I don't know what to do. I'm feeling suicidal and I'm scared. I can't do this anymore. It hurts so much. I feel so stupid for even getting this low.