Why not look at sex as a gift. Two people giving physical, emotional and sometimes even spiritual pleasure to each other. The past is gone, what matters is the present. I think what is missing is the ability or willingness to fully receive. Instead there is taking. If something or someone is received, it will give rise to an overflowing of gratitude and a complete circuit is made. When you take something there is no gratitude.
I am sure there are hundreds of millions of wonderful ,loving, intelligent men in this world who would be thrilled to marry a woman who sparks their deepest heart, no matter how many sexual partners she has been with.