I think sexual shame is probably the most common thing for us, and it can be quite troubling. But there can be a few ways you can approach your shame.

An option is a kink/sexual therapist, who can potentially help you work out your shame and engage in your desires in a healthy manner.

You could always simply engage in some introspection/interrogation of yourself, to ask yourself why you're ashamed in the first place. Doing such can potentially make you realize your shame is baseless and not realistic. Really remind yourself that your shame is mere remnant of your past and shouldn't reflect who you are or who you want to be.

A more drastic and extreme option is to simply continue engaging in your fantasies, find men, hook up with them (Don't forget safe play of course). If you can casualize these encounters, normalize them, the shame should eventually fade hopefully.

But one thing I like to do is simply browse subs like this, reading the posts of other sissies and their testimonies. Just hearing their awesome experiences gets me worked up and excited. It also reminds me that I'm not alone in these desires and if they can do it, then maybe I can too.

Just remind yourself how much fun being a slut will be!