Is he cheating or am I over thinking?

So when I first got with my husband things were great but he had not long got out of a long term relationship he clearly hadn't healed enough anyway he started acting funny with his phone being secretive with it and I found out he had been messaging his ex asking her back (she told me I didn't snoop) well I found out I was pregnant and we decided to work on things and made it work. Well now he's started acting funny with his phone again he won't even talk to his mum on the phone around me he always goes outside for a cigarette and makes his calls then without telling me anything (obviously I don't need to know everything but it's a change so it has me thinking) well this past week he kept getting calls from a no caller id and he refused to answer whenever I said his phone is ringing (he doesn't usually answer numbers he don't know so not overly off) well I told him next time I'll answer for him if he liked so I did well I heard a TV/music in the background so wasn't any form of company and was clearly a regular person . They heard my voice and hung up. I said to him that is very odd they heard a woman's voice and hung up and have not rang since. He said yh they've rang different times of day all week which to me rings alarm bells they must know him as he works 3 shifts so to it seems they know this and trying to catch him not knowing what shift he's on.

Am I over thinking this or is the calls strange ?

I know the pin to his phone but he has it on him all the time so I can't go through it plus he deletes everything. I went through his phone once after seeing an inappropriate message and since then I see out the corner of my eye him deleting things I question him why he's deleting things and he denies it

Answering "k" it was me who had been trapped I told him I wanted an abortion and didn't want to be with him he is the one who wanted to keep the baby and work things out and I felt like I couldn't terminate knowing he wanted the baby so I agreed