You can start Plan A. Read on this website about Plan A and what it entails. Sometimes when they say they are no longer in contact, they just go further underground. Be alert and vigilant to what he is doing.
Ask for his passwords to work emails, and install a keylogger on your computer when he is gone.
Look at the "Spying 101" thread on this forum.
Give him Joseph's letter. You can find a copy of it in the "notable posts" thread in the "Just Found Out" forum, right up at the top.
Know that you can change yourself, but not him. Know that you control only yourself in this relationship - but that by controlling yourself, what you do and say, and improving yourself, you CAN improve the marriage.
Know also that his affair is NOT your fault. No matter what he says or does, the choice to have an affair was HIS.
The state of the marriage leading up to the affair was both of yours, 50/50.
And it was NOT a solution to marital unhappiness, marital discord, or marital difficulties to have an affair. Being "stagnant" in a marriage does not excuse an affair. Being "bored" does not excuse an affair. Needing attention, needing more sex, needing you to be jealous, needing ANYTHING, is not an excuse to have an affair. His affair was wrong. And don't let him call it anything else. Don't use the word "relationship" - use "affair". Every time - because if you allow him to rephrase and reframe the issue into a "relationship" he WILL. It was and is an AFFAIR, and use that term.
The weekends are slow. More help will come along.
SB