Advice please

So the last couple of weeks I’ve noticed my mans been acting abit different...

Spending a lot of time on his phone not really showing me any affection etc...

Well I’ve noticed his been speaking to the same girl on snapchat Everyday... I’ve never seen the messages because he don’t save them and I don’t want to go through his phone...

I just have this awful feeling that she’s the reason his acting so different with me I’m 28 weeks pregnant and I’ve put on some weight and I know I probably look very unattractive

I don’t want to ask him because for one I know I won’t get the truth anyway and two I don’t want to look crazy

But I feel so rubbish about myself now..

I had a really bad relationship with my ex where he cheated on me over 20 times am I just being paranoid? Because this feeling I have has never been wrong in the past 😩

Help please I’m so confused right now 😂😂