I know this thread is old but I wanted to reply anyway...

I doubt you'll be able to keep this sort of thing a secret forever - are you completely unatteacted to your husband? Has he started questioning the situation?

I know if I was in your shoes I'd rather tell him before he found out otherwise...at least it shows you trust him enough to tell him the truth. He might be surprisingly accommodating....you've already had an affair though and if you plan on telling him this too I would be prepared to give him some space.

If you're actually happy in your marriage and are just having difficulty with sexual needs perhaps discuss an open relationship? Sometimes this works better than a complete marital breakdown. It might be a long shot but perhaps it's better than the alternative...I know of at least two people who have remained married but seek sexual satisfaction elsewhere. It's difficult to pull off I agree but you're only other option is to end things - and it would be fair to your husband, especially if you no longer want to be with him.

Just tread carefully and once you've decided what course to take stick to it...good luck.