I've made a terrible mistake, can it be fixed?

I am a middle aged woman in love for the first time. I believe that the man I am in love with feels the same toward me. However, when I spoke to him regarding his intentions for our relationship he responded that we could only be friends because of our professional relationship. I was very hurt and felt utterly rejected. I was certain that this was an excuse and that he truly was not attracted to me. I was tormented by these feelings for months. During this time the best friend of the man I'm in love with was very kind to me and eventually expressed an interest in me physically. Since I was feeling so rejected I was very flattered and comforted by this attention. I began a ual relationship with this man. Now the man I am in love with seems to be reconsidering his decision and the man I'm sleeping with appears to be becoming attached to me and possibly falling in love. I don't see any way to extract myself from this mess without hurting everyone involved.