I am so sorry for your struggles. I cannot imagine how it must feel to be so betrayed in such a way. Have you attended marriage counseling or a
Retrouvaille retreat? I would suggest looking into those. If he is unwilling to attend, individual counseling may be helpful for you to learn how to cope with your current situation.
This is a really tough situation because it sounds like he didn’t just make one mistake, but simply has complete disregard for your emotional and physical health. You should make sure you are clear of STD’s, and for your own safety, refrain from having sex with him, since you never know how many women he’s slept with, what what diseases they may carry. Condoms are not foolproof, nor are they morally permissible in Catholic teaching.
Also, since he is a serial adulterer, there is a possibility that he may never have intended to be fully faithful to you, even when you got married. Do you know of any transgressions he may have committed before you were married? Did he state his vows without really valuing marital fidelity? Note: I am NOT advocating for you to get a divorce and annulment, simply stating that this is a possibility.
We don’t really know much about your situation. Are either of you Catholic? If you are, then you should speak with your priest about your situation. A good, orthodox priest will be able to give you much better advice than us anonymous internet posters.
I will say a prayer for you and yours, that all may work out for you according to God’s will. God bless you both.