Hi there ~
I understand your concerns. However, you may not know if your husband is bisexual unless you confront him with these questions. It may also be helpful to ask your husband to go to therapy with you if you find that there is suspicion on your end and that your husband is denying bisexuality. I strongly advise you to take the expert help of a sexologist
or a psychiatrist
if you have problems persisting. I hope this helps.
Take care and have a lovely day!