I think it's very important to remember what she said to you, "I love you, BUT, I'm NOT in love with you anymore." I don't think she loves you and without trust and love in a relationship...there is no relationship. I recommend that you talk to her first about your concerns and see her reaction and response. I also recommend a marriage counselor, talk to a priest who are trainned for these issues and remember that there are children involved and you want to make sure they are protected from what is going on between both of you. Good luck.
I would imagine that your sense of emotional attachment with your ex has been damaged by the betrayal of trust (cheating). So, maybe when your with her, you're already resigned to the fact that the relationship is over; and, your feelings towards her are no longer as they once were. Such emotional "shutdowns" can understandably affect one's sexual motivation.
But, if you don't mind my asking, why are you involved with her, now? ...especially,
after she's cheated, divorced you and you are admittedly "attracted to other people."
And, what of this other man with whom she was cheating on you?
Is she cheating on him with you?
Just wondering!
This is completely normal under the circumstances. Getting past a cheating spouse is tough! There will always be thoughts in the back of your head and the "what if"
My question to you is, why did you get back together with her? There was something lacking in the marriage for her to look elsewhere (for her anyway) and there is a pretty good chance that it will happen again. Especially if you have forgiven it before.