is he cheating?..

so, my other half claims to have a work meeting this evening, at 20:30, and it can finish at 22:30-ish, depending on how it goes. then its an hour's drive home.. we've had a few trust issues in the past, but he told me today that he 'JUST' received this email, without me saying a word he screen shot it and sent it to me? but it was from last night? not just now? I told him that I've seen the time at the top of the screen shot, he went BRIGHT red and said he just 'forgot' to tell me last night. he had this one 'friend' who we fell out with due to her being so needy, & being over 'friendly'. I think he's meeting her, and I feel sick to my stomach. 🤢 what do I do? *been together 5 years*