I was his second girl?

I've known him from work i was never interested cause i didn't wanto risk falling in love again.. but i risk it , and we've gon ut a few times, yes we were sexually active and he was such an adventrous guy i became attached to his ways he treated me so nice come along way just to pick me up see me veryy kind indeed we laughed after sex during sex in the ca every where but.. saturday last week me and him went to a beach party at first he didn't want to go because an ex girl of supposely was going to be there.. at that time i already suspect after i convinced him to get out (mayor fight) we sat had some drinks etc... then the ex girl came with a friend of mine in class imediatly when he saw her he went f to his car.. after that i saw the girl heading his way after a few minutes the girl in my clss told me her friend (the ex was also his girlfriend) i was shocked... no it's been 4 days i think and he only called me 2 times today and the night i found out.. i mis him extremely but i don't wanna go backk to him cause i feel bad for the other girl which he seeing fo 3 years and me only a few months.. soo if you were in my situation would you call him back cause havn't i'm trying to get over him. get my feelings out so i want take him back anything i just wanted to know what wuld you do?