This guy lied to me and told me I was his girlfriend but he already had a girlfriend...?

Im so hurt right after I slept with him, his roommate says have you called your girlfriend and I ask him over a millions times before do you have a girlfriend and he would say no only you baby. Im so hurt I feel so low about myself because people who I give a chance only end up hurting me any ladies or guys can give me advice you feel like can help. Thanks