Charrua, there is nothing " sick" or "not right" about this, there are many men who feel like you (such as myself) with some nuances. I find nothing wrong in being turned on by other men desiring the your woman and the woman you love being pleasured by others besides you. It could only be considered as "immoral" perhaps but it is pretty common.
About changing your mind after ejaculation, it somewhat describes the post ejaculation syndrome but since it lasts only for bout 15 minutes, it shouldn't be considered as syndrom but decline. Unlike most women, most men have a sexual decline right after ejaculation. The guilt "what the hell I was thinking" is just the moral conscious imposed to you speaking. Let me tell you, being turned on again after 15 mins is TOTALLY NORMAL... And if you ask me, do NOT change the way you think, but try to explain to her (but first of all yourself) the logic of immorality, why you are turned on by this, why you want her to experience pleasures with others.
I am pretty much in the same situation but I am not confused at all anymore, so if you ever want to discuss, hit me up.
Best luck..