My mom chooses her bf over me. Is this normal?

I’m a 17 year old (f) and I need to know if this is normal for adults and whether or not I’m over-reacting.

My mom is dating someone. I like him a decent amount. Truth is, I don’t know him well enough to have a decent solid opinion. They’ve been dating on and off for about 3 years now. On and off. It’s exhausting, especially since I always have to hear about it. My mom and I are extremely close and often see each other as friends. Of course, there’s still the parental boundary that we never cross because truth is, as much as we act like it, we’re not friends. We’re mother and daughter.

Anyways, this is the first guy my mom has officially dated since her and my dad broke up when I was 9. I’m happy that she’s happy, but my issue is the fact that I feel ignored. Whenever he comes over, I’m not really allowed to hang out with them. She says I can since it’s my house too, but usually if I try to go in the living room with them, they’ll go into her room and lock the door. I get that they need privacy sometimes, but I want to be able to see my mom. It’s almost every day that they do this. And then I’m stuck all alone in the living room by myself. He also has a son that’s younger than me (11) and he’ll leave him alone at their place to come to ours which rubs me the wrong way. Whenever he doesn’t come over, I’m kinda glad because I want to be able to spend time with my mom. But i can’t because he calls her non stop and they’ll talk for hours and she’ll ignore me and close the door to her room and if I go in to try to ask her a question, she gets upset. Also, when they call they almost always get into an argument and i hate to hear fighting because I have trauma from when I was younger and my parents would constantly yell and put me in the middle of it all.

Back to the on and off thing…. They break up like every 2-5 months. The longest they lasted was about 9 months. This has been going on for 3 years. There was a point in time where I’d be at my moms and they’d be together, I’d go to my dads for a week, come back and they’re broken up. I go back to my dad’s for another week and they’re suddenly back together. It was like this for months. It got exhausting cause I’d have to hear about it.

Anyways, they broke up around thanksgiving but they got back together briefly during the California wildfires in January because he was in the thick of it and my mom let him and his kid stay with us. Right after the fires, they broke up again. During the time that they weren’t talking, my mom loved to spend time with me. Once again, I was her favorite person. She’d hug me more, watch tv with me, and we’d just hang out. But then she unblocked him and now I’m an afterthought. She asks my dad to keep my for a longer amount of time because she want’s to be with him without having to deal with me at the house. My house where I live. Not him. Although he’s trying. He keeps pushing for them to get married, to which my mom says that they don’t even live together. He says they he’ll move in, and she keeps saying no, thank god. It feels like he has no regard for me and my older brother (23). We live in a small apartment. My older brother and I share a room. If he moves in, he’ll bring his son. That’s 3 kids in one room. And even if we do move, my mom makes more than he does but it still wouldn’t be enough for a 3 bedroom, let alone 4 bedroom. That means hypothetically, best case scenario, either his son would get his own room while me and my brother are forced to keep sharing, my older brother and his son would share but they‘ve had like 2 conversations and theres a big age gap there, or me and his son would share. And his son gets on my nerves because he‘s immature for 11 years old which is saying something.

I’m rambling…

Anyways, it’s just exhausting. I feel neglected whenever they’re together. Like I’m an afterthought. Normally, I wouldn’t mind about having to stay at my dad’s, except the last 8 months, my father hasn’t been speaking to me. I’m all alone when I’m at his house. And she knows how damaging it is for my mental health when I’m here. I even ask If I can go home and just stay in my room, which I shouldn’t have to do, but she says no because she still has to worry about feeding me and making sure I‘m safe if I go out but I feel like that’s the bare minimum.

Is this normal for parents or is my mom’s genuinely favoring her boyfriend? If so, what do I do? I tried bringing it up, but she says I’m being dramatic.