He thinks there was no need to tell me.

My boyfriend went back to school for nursing he is 38.At the end of a lab class before he got into nursing program his married female lab partner ask to stay in touch.He said girlfriend wouldnt like him giving phone number out.So week later she says I want to know if you get in nursing and what classes are like can I have your email so he gave to her.I didnt know til he stopped emailing her like two years later he emailed every few months he answered her questions.HE says itwas no big deal to tell me.He wasnt calling or instant messeging just a email every few months.He also sold his summer book to her meet in a parking lot I didnt knowHE didnt tell me.Said it was to sell a book whats the big deal?What do you think?