A Married Woman Keep Sending my boyfriend Naked Pictures

This girl who works with my boyfriend sent him a bunch of naked pictures. She's married, has a baby, and she was fully aware that I am with him and that I'm pregnant. She's about 5 years older than my boyfriend, and I'm two years younger than my boyfriend, so she's quite a bit older than me.

My boyfriend says that he didn't ask for them, but she sent them to his email address, which he said he gave to her just because she asked for it. She's in a manager position. He quit his job after this incident.

I've been with him for over two years, so it's hard NOT to believe him. He's never done anything to make me think he would cheat on me, up until now. He swears that he never did anything with her, never asked for the pictures, didn't know she would send them, etc. But what's strange to me is A: that he gave her his email address. B: that all of the pictures were opened. And C: if he didn't want the pictures, why didn't he tell me that she sent them?

I found them by signing on his email. He didn't know I had his password. I knew it because he uses the password for everything. He had not replied to the emails, but he opened all of them. (Each one contained a different picture.)

He said that once he saw them, he went to work the next day and "told her off.": I'm finding a lot of this hard to believe, but I WANT to believe him. I'm 30 weeks pregnant and don't want to be going through a breakup right now, but I don't think I should be with him if he's lying to me.