If this obsession is really so strong as to torpedo relationships then what is the harm in his talking to your boyfriend about it? Maybe a civil conversation where boyfriend gets to explain "I'm flattered that you're in to me, but I am not at all interested. Sorry man, you've got to let that go" to your husband would be helpful.
I did a quick search:
Very often in life we don't get what we want. We need to learn to not let it consume us and damage parts of our life we *can* have.