I know how hard it is to deal with this feelings initially. I hid my feelings for another man for over 3 years until I couldn't deceive myself any more. I manage to do so because I didn't want to admit to myself what the truth was. You can't go against your feelings and even if your husband is mad at you for falling in love, be sure to get things clear: He can try to or wish to forbid these feelings but how successful will this be? I think that MichelleZed is absolutely right, you missed the starting point when thing got serious you didn't 'fuck up' up to now in my opinion. Try to get the things you want, your husband wants and 'the other' wants clear and talk about it.
Some words of encouragement: My husband reacted a bit cooler than yours when I confronted him with my emotional mess but I think it is possible to sort this situation out. We pulled it off and are still happily doing the work that it needs to be taken further. Good luck.
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.