Stuck between

I am 21 yr old (M) , currently dating a 20 yr old (F) . We are in a relationship for about 2 . 5 yrs together. When we started dating out of loneliness i got attached to her , same goes for her aswell . Firstly i didn’t cared about the looks, thought looks could change after time . But now I think it does matter to me . I met a girl at my gym , i found her attracted and she is too interested but the problem is should i continue to date her or should i just break things up and start from the beginning. I know if i wasn't matured enough to handle things at that time . Now my current partner is obsessed with me , and I m feeling guilty of leaving her behind aswell

Please help