Angelstar,
First of all it helps if you are excited to begin with, so do some other things that you enjoy first. (Often at the beginning of a session I am thinking "no way am I going to do that today" but I change my mind later on in the session when I am turned on) Once you are aroused, try it first while on your stomach. Try to relax and youdefinitely need to be the one in control the first time.
Slow, gentle play is best. Start small get bigger slowly, one finger, then two then a small dildo them a larger one and combine it with plenty of clitoral stimulation and lubrication so it is enjoyable.
As far as the cleanliness is concerned, it has never been a problem for me, even without an enema. I am always clear if I am prepared carefully. It seems my body knows what's coming. (pun intended) You may be the same way.
If your partner really enjoys the anal sex, though. He probably expects things to be a little messy. Don't worry about that. It is his choice.

PS Enemas aren't bad at all. You might find them to be enjoyable.