Pregnant, checking out. Advice?

Long rant, need advice: I'm really struggling and would love to get an opinion if it's simply 18 week pregnancy hormones, or if I have any justification in my feelings. We (partner, 3 year old and I) just got home from a "beach vacation" in Port A with Boyfriends parents, brother, sister in law and two Children, ages 3(boy) and 4(girl).To start, we get there and have the worst room, on the second floor where the main living area is. The bed squeaks, laundry that SIL decides to run at all times can be heard from this room, loud fun nights of drinking, hallway lights and niece/nephew screaming can all be heard.Second, SIL makes a point to discuss how she likes second child- boy- better. He has had a heart condition and is spoiled rotten, based on how he acts the entire trip.Neither kid is on a sleeping schedule. Any kind of schedule. Niece LITERALLY screams for about 45minutes- an hour EVERY night around 10-11. Our bedtime is around 8, 845 on a late fun night.FIL only seems to want to correct my child, which seriously started grinding my nerves.We gave Nephew his birthday gifts and they were all playing with the toys. Nephew got upset that My son was trying to play with him and yelled at My son that he wasn't a nice boy. My son looked up at me and partner, and said "am I not a nice boy?" This LITERALLY happens daily, at least 2-3 times. The excuse? Oh our kids are assholes.The absolute final straw: last night, the fire alarm starts beeping at 945pm. No one is cooking, no fire, nothing. It continues to do this on and off about 5 times each time for an hour. FIL decided to call the rental place instead of the fire department. I recommend that maybe we just call the fire dept to have them come check, to which he replies "why would I call the fire department if there's no fire 🙄" Rental girl comes out to say oh we will replace the batteries. Mind you, different alarms are going off on all three levels of the house. They replace the batteries, which works for a few hours. Only to go off again at 154AM right as I was about to fall asleep. Who wakes up? None other than screaming terrified niece.Partner seems to think nothing of it, but after seeing all of the interactions, I'm totally sad. I grew up feeling like a "second rate" sibling in my family, and I don't want that for my son. "They're just kids" is his excuse, but that can NEVER be the excuse with our son..I also don't want to ever leave my son with FIL as I seriously don't trust his judgement.Rant over, but would love to hear someone's perspective. If it is just hormones, I'm happy to admit it and move on. The first 3-4 days I felt like it was just hormones and moved on. The last 2? I couldn't help but remove myself from the situation.I feel like checking out of this relationship, and feel like "not caring" is the answer, but i just feel hopeless.Help a struggling mom!! via /r/Parenting http://ift.tt/2ugmJA5