Having good sex is a combination of connection and learned skills. If you have no experience you have not learned the skills to give and receive pleasure. If you have no connection (i.e. choosing a "random girl" to sleep with) all the good feelings that can come with sex will be absent. If you find someone you connect with and are willing to learn what you can do to give you both pleasure, I'm sure it will be fantastic.

What I see in your post is that although you may have let go of your religious background, you still are holding on to the moral judgments from that background. Is it possible that a woman is not dirty for having had sex with another man? It may be helpful for you to examine where the feelings of disgust come from.