Dog driving me insane!!!

I have a 4 year old hound/pit mix who I love to death. He’s the sweetest thing ever. We adopted him as a puppy at 12 weeks old. We had issues potty training him and he never tells us when he needs to go out, we just learnt to get him on a good schedule going out every 4-6 hours. he would pee in our house occasionally if there was a storm or if we didn’t stick to his schedule. We got another dog about 2 years ago and that just about fixed all the issues and he hadn’t peed in the house since.

Back in July I found out I was pregnant. I was super sick for about 10 weeks and just miserable but we still stuck to his schedule. In August he started peeing in the house again. Maybe once every week or so. Flash forward to October and it’s turning into multiple times a week. My husband and I went to the beach for a week and had my dad stay at our house to watch them. The dog never once peed in the house. And my dad didn’t even follow his schedule. As soon as we get back he’s peed everyday that we’ve been home. This weekend I spent the night at my sisters. And guess what. He didn’t pee in the house.

Im now almost 18 weeks pregnant and I can’t have this keep happening. We have tried everything. Walking him, taking him out multiple times to pee, withholding water at night and I don’t know what to do. He only pees at night so weve never been able to catch him doing it since were asleep. I’m convinced this is all because I’m pregnant and he’s acting out. Has anyone experienced anything similar? Or have any ideas on how to fix it. I’m going nuts.