My boyfriend became very distant yet attentive at times when I was pregnant last year.
He started spending a lot of time with another girl. During this time as well.
I wasn’t aware of just how much they would text while he’d be at home.
I felt something wasn’t right he’d be so sweet but yet I felt he was so
distant. He’d always reassure me how much he loved me, how there’s nothing to
ever worry about when it comes to him and other women. He knew I didn’t like
it when he’d hangout with her. It felt at times he’d chose her over me but
he’d always talk negatively about her though and felt as if he were just
doing it for me not because he truly felt that way. It wasn’t until 3 months
ago that we started to talk about all of that. He assures me nothing ever
happened he never felt that way about her. That there was once where he said
something along the lines of this makes me feel turned on is that normal does
it happen to you? And that he once said he can’t even run one out in his own
house how sad is that. She never saw him that way either. But I feel he’s
holding back that he’s down playing it even though he says he’s not. I just
want to know exactly what would they talk/text about and what were/are his
feelings towards her? What exactly was going on between them? I’d really
appreciate your help please

He was reacting to the stress of being an expectant father and using her as is sounding board. This is more common than you would think. He did have an emotional relationship with her, but was more attached to you. She liked him more than he liked her. He just wanted someone to vent his stress to and he liked the attention of a woman. It was good for his ego to have someone who wanted him.
He did distance himself from her, so dredging up the past is only going to damage the relationship. I know this hurts you, but I do feel he was physically faithful to you.