I too had guilt and shame issues when I realised that I was sexually attracted to men as well as women. One of the things that was so difficult for me was that in society, one is expected to be "gay" or "straight", and "gay" carries its own stigma and is often best hidden. It was clear to me that what I felt wasn't acceptable- a common comment from gay men was that I was "transitioning" to gay and would soon loose my attraction to women, but in my own mind I was sure of my sexual attraction to women and I continued to be after my initial experiments with M2M sex. Add into the mix some unpleasant initial experiences with men where transactional anal sex seemed to be the goal, and I was a very confused and ashamed person.
I found the guilt and shame to be so overwhelming that I got to the point where I couldn't enjoy any sex because I wasn't comfortable with my own sexuality; I didn't understand it and I didn't understand how to make things work for me because what was real for me seemed to be a sexual dead-end.
What clarified things for me and made the guilt and shame go away was responding to a customer's sexual comment; after I responded positively he helped me to fully explore my curiosity in my own time without pressure. I learnt within about 10 days of intense afternoon sex that I really enjoyed man sex and men's bodies. The experience that cemented in my own mind my attraction to men could be rewarding and pleasurable, the guilt and shame melted away from there.
It was quite some time before he introduced me to anal sex (outside rimming) and I again found much shame and no pleasure in butt stuff; it seemed dirty and pointless. With encouragement, it took me about 4 weeks of spare time with a dildo and vibrator to enjoy anal stimulation but once I got to that point the shame disappeared entirely and I became a dripping mess when receiving cock, twice an afternoon at least 5 afternoons a week at times.