GF won't have sex w/me but would w/ new bf
My open relationship with this girl is one of the best things that happened to my life. However, a year into our relationship she decided she won't have sex w/ me saying that it felt "unnatural" for her. Her mind is ok w/ it but her body doesn't feel the connection. Last month she admitted that she has a new bf and has sex with him-- because it felt natural for her doing it... with him.
Although we still kiss, cuddle and even sleep regularly together, we do not have sex. I still enjoy being with her and wouldn't consider giving up our relationship. I do have sexual encounters with other women but it was nothing romantic. I really miss having sex with her and I don't really understand what's exactly natural and unnatural for her.My sex with her is the BEST and the most fun I have experienced among all the partners I've had.
What is it that I'm not getting here? Help!!