Quote: I feel that it's slightly dirty - a really stupid thing I know and I hope to purge myself of that.
Welcome aboard, Jen. The first thing is to stop saying critical and judgmental things about yourself. Don't call yourself stupid. This mental/emotional/physical system that we call "Us" is very loving and very smart and the ultimate purpose of all of your feelings is for your own safety and well-being. Some of these old, old feelings came to be and got set in concrete when we were very young as a way of protecting ourselves or because we misunderstood something or were frightened. Unfortunately many of us are living with those decisions today that we made when we were three years old!
Instead of saying you want to "purge" yourself of this idea or feeling, as though it were an enemy or some terrorist stowaway, you might do better to befrend that part of you that feels sex is dirty. To tell her that you love her and you know she feels that way for a very good, but possibly no longer relevant, reason. Don't expect a shift on this right away, but if you're patient, gentle, and quiet, you may get some internal thoughts or memories that can help you untangle this thinking/feeling. Picture taming a semi-wild kitten that has wandered out of the woods to your back door. It may take a while, but if you're patient and welcoming, this part of you will reveal itself, and I'll bet ultimately it will be willing to change. Therapy is very well advised for you and your husband.