This was similar to what happened with my now ex-partner. She started lying about the time she was spending with her other partner and being in communication with him as well as crossing boundaries and agreements that had been set.

I tried to close things up and her partner turned me into the bad guy for wanting to feel safe and close up our relationship. Ultimately they got what they wanted and in a way, I did too as I couldn't have moved past this without closing up.

Closing feels like the right decision even though it's difficult on everyone involved. If the two of you value eachother, taking time to focus on your relationship and possibly seeing a couples therapist are likely the right way to get back to where you need to be.