Feeling betrayed

Hi everyone,

So, this weekend my boyfriend of 9 years, father of my son (& I’m currently 31 weeks pregnant with his second) went out and came in at 4am.

Just before he got in I heard his iPad “ding” so I looked and was mortified to find messages to another woman asking him to go to hers (which he didn’t do) but he’d replied saying “next time”.

I questioned him immediately & he said it had just been some silly flirting but I feel like he’s cheated on me. It feels like there was intention there to do something in the future. I feel completely betrayed by him.

What does everyone think? I’m am being over sensitive?

Thanks