I'm not exactly sure what's killing you. At first I thought it is the guilt you feel over your feelings. Then, I reread your letter and it felt like a train with broken brakes is barreling through a station and there's no way to stop it. Then I began to wonder if you're so upset because you feel unable to stop yourselves.
The first thing you must do is become clear on what you want. You didn't say that you love your husband. You didn't say that you want to stay married or that you're concerned to ruin your marriage. All you said is that you're no home wrecking whore. This sentence tells me that if it weren't for your sense of guilt and morality that you would pursue this man and even end his marriage.
What about your own marriage? Do you love your husband? Do you want to keep your marriage? I have to wonder if you are open to this budding infatuation precisely because something is wrong or missing in your marriage. You could say that this attraction is a messenger that 's been sent to urge you to take care of business at home.
Find out why you are looking elsewhere. What is it that you yearn for from the doctor. That's what you want in your marriage. Tell your husband what you want. If you try and the marriage doesn't improve or if you discover that you don't want to improve your marriage and, in fact, want to end it, then you're free to do so.
then your path is clear. Accept that your feelings of attraction to another man are normal, but tell yourself that no action is possible. The relationship with your doctor must be strictly by the book. The fact that your doctor paid for some of your tests was above and beyond the normal call of duty. I'm afraid that this fostered your feelings for him and made you begin to think that he cares for you personally, which I'm sure he does.
But, we don't know if he's unhappy in his marriage or on the verge of divorce or simply attracted to you.
If you don't want to stay married to your husband, then the only path is for you to end your marriage, make yourself free, and let fate takes its course. This would be the only honorable path for you to follow since you wouldn't be leaving your husband for another man, you'd simply be leaving because the marriage is irreparable.
f the doctor decides to end his marriage and makes himself a free man, then you both can explore whether you are right for each other. If he makes himself free first before you become involved, then you're no home wrecking whore.