There are a couple of things you need to understand, and REALLY understand deep down to your core what you are about to do.
What I read from you is that you had been thinking about this BEFORE Dday but didn't schedule it until AFTER Dday. I get that this is something that you've wanted to do but it sounds like your timing is just off.
What I'm reading is desperation from a BS who is trying to be more desirable than the OW.
Amber....this surgery can be put off. You are only 4 months out and granted I haven't read your profile but nowhere have I read if your WS is remorseful and trying to work on the marriage. Are you two going to counseling? Just where are you in your relationship?
Hell....you are still losing weight on the infidelity diet. Have you talked to your Doctor about what is going on in your life? The stressors?
I'm in the "re-think this" camp. It smells of desperation. Work on yourself and your marriage and if things go well then get the surgery. Don't do this to try and keep your WS or to prove something to the OW. Have you sat down and REALLY asked yourself why you want to do this right now? Do you really get that it doesn't matter how great you look, if your WS is wanting to cheat he will do so. We have drop-dead beautiful BS's here. People who you look at and wonder what the hell their WS's were thinking!
The way you look is not going to keep a WS from cheating. There is something broken in them and they need to fix it.
Wait. Work on yourself and get to a good place.