The solution is all in your final sentence. The guilt is killing you, you desperately want to relieve your guilt and now you are wondering whether you should tell your husband, so that you can relieve yourself of some of that personally poisoning guilt. The answer is NO. You've cheated on your husband and that was your choice, there is obviously something wrong with you and the relationship, because happy, fulfilled people in great relationships do not feel the need or even think about cheating on their partners.
Whatever you did, make your mind up. Leave your husband or leave this man, you cannot possibly have both, that's very greedy. It will also end up killing your relationship with your husband, even if you think it's good for you.
Don't tell your husband, that's the most selfish thing possible, it's nonsense to think that the honesty will do him any good at all, it will destroy him inside and you will just make yourself feel better at his expense.
Why do you feel guilty? Think about that? You feel guilty because you like what you are doing and you know it is wrong and you are not strong enough to do the right thing.
Whatever you did, make your mind up. Leave your husband or leave this man, you cannot possibly have both, that's very greedy. It will also end up killing your relationship with your husband, even if you think it's good for you.
Don't tell your husband, that's the most selfish thing possible, it's nonsense to think that the honesty will do him any good at all, it will destroy him inside and you will just make yourself feel better at his expense.
Why do you feel guilty? Think about that? You feel guilty because you like what you are doing and you know it is wrong and you are not strong enough to do the right thing.