I think first you need to decide that you actually want to stick with your current girlfriend or want to go with new one.You said that you don’t want to cheat your current girls friend but when you are getting chance to do something with other girls you just run with thing more so don’t you thing ? it is also cheating.I believe that if you had some relation in past that is ok but now after having such good relation,if you are looking for other one that not good.