@Gaga1234 sorry to read this, the way you lay it out unfortunately it feels a lot bigger than a few white lies. Clearly there’s a much broader context that’s hard to get across on a forum post but on the face of it, I think you have serious cause for concern. No need to panic though, there’s no rush and if there is something up it really is best to find out as soon as possible.
The first worrying thing is that he’s talking to you like shit since the baby arrived. I’m afraid this is quite common amongst men with an abuse mindset, when a situation changes this can be the trigger for abuse strategies. It can happen when people move in together, or that’s fine but the thing that changes the dynamic is marriage, or as in your case a pregnancy and new baby.
Next of course is the lying, but he is also essentially confessing to you too (or he’s testing the boundaries for how much you will ignore in future) that he intends to sleep with people in New Castle. He says the only reason men want to go on stag dos in Newcastle is to sleep with other women, he’s trying to go to Newcastle, you need to take him at his word. The work thing is clearly coming from a similar mindset.
Liking other women’s posts, this is not good, he is looking for someone else to sleep with, he’s doing it publicly and he felt he was “caught” so he deleted the account. I would be very surprised if he hasn’t created a new account under a different name to do just this.
You are not being petty from what I can tell, you are trying to be reasonable. Unfortunately, you can’t ignore this long term, the “big lies” are here already. If you are determined to hold on to the relationship, there are things you can do, I’m not sure this is something that many will recommend- there is a good chance his behaviour will get worse and worse.
Can I check, given that he treats you badly at the moment, do you really want to be with him?