You are both still married and living at home together? Would spending the night out be normal behavior any other time? Why would she spend the night out now? What is your gut telling you?
You need boundaries here.
M22,H45,W45 S21/18D12 Retain faith that you will prevail in the end, regardless of the difficulties and at the same time confront the most brutal facts of your current reality, whatever they might be.