Separation agreements, changes in the law

I have been divorced for 11 years after a 30 yr marriage. At the time we signed an unincorporated separation agreement.
We both decided to purposely leave off clauses regarding alimony of cohabitataion or remarriage as a reason alimony would stop. Only a stop date.
My exhuband is with a new woman and now it seems my exhusband is trying to accuse me of cohabitating.
I dont think I am–I do see someone–
Regardless, can he now try to stop due to the claim of cohabitation if it is not in the agreement?

If the contract is silent on cohabitation then he can’t stop paying for that reason.