unsure what to do

So, tonight my husband and I were laying in bed on our phones like normal. I looked over and noticed he was in some sort of messaging or text thing so I asked who he was texting? He told me it was a girl he went to school with and actually dated but she is now a lesbian in a relationship with a woman. No biggie. He said they were talking about scentsy as she is a consultant and we've asked her specifically about product before. Anyway, I'm now laying on my side facing him and trying to see what they were chatting about without looking too nosey.  I read something he said about his grandma turning 70 in January, again no biggie. Then I saw where she asked what time we'd be in tomorrow (another state). He replied I just depends on the weather blah blah blah. A few mins later I saw her ask if his wife knew they were messaging. He said yes. She said ohhhhh. And then she said something like "you just said my pussy". My heart sank. He didn't reply right away. He got up and went to the bathroom....I'm sure to say whatever it is he needed to say. Im crushed but have no idea what to say. He claims they were talking about her adopted son. I want to look through his phone but I'm afraid of what I'll read. Rewind to the beginning of the conversation and he said she may still not be over him, bc at some point in the conversation she told him the exact date that she lost her virginity....to him. I feel so sick to my stomach right now and I definitely can't sleep...