DH and I have been together for 12 years, married for 7 and have 1 child together and 2 older kids each from previous marriages. We've had ups and downs but overall we have a fairly passionate relationship (sex a few times a week) and I think love each other. DH has a very flexible teaching (at university) job, however, nearly every Friday morning he claims he has a meeting and disappears from around 9.30 to 2pm when he resurfaces. It could be completely innocent but he never checks his phone during that time (I can see from whatsapp) and goes every week even out of term time when there are no lectures. He's always quite vague when I ask him where he is doing and says it's a meeting to do with his research group (which I know exists) but I am still suspicious as it's always Friday mornings and he is always completely offline. By way of background, DH's had a long affair with another woman during his last marriage who was a student (a mature student) at his uni which is raising my suspicions. I did try to pin him down about the meetings once but he got angry that I was suspicious and said I had no reason to be. What do I do? Let is go?