Help! I am in desperate need of advice.

I am currently in a relationship with a man who has a two year old son.
I have absolutely no interest in children, If anything I've always felt extremely awkward around them and I am unsure if I ever want any of my own.

This situation is tearing me apart, I am in my early 20's and feel very uncomfortable playing this role. From the offset I explained to my boyfriend that I've never been fond of children and that him having one would be a huge issue for me and one I could never guarantee I would get over (meaning that we could break up over it as I did with my ex)

I find myself dreading his son coming to stay (every other weekend). we only have a one bedroom flat so his son has to share a room with us which means that from about 8pm when he puts his son to bed on the Friday and Saturday of every other weekend my bedroom is off limits to me, my boyfriend won't even let me tip toe in to retrieve a phone charger or a book as he says I'll just wake him up, in fact if I even go to leave the living room I get constant reminders to stay quiet and not turn the light on etc. this also means his kids bed is constantly in the middle of our bedroom, there are plastic light up stars on the walls and a painted Disney character, I feel like it's not my room at all, I spend 0 time in there, my boyfriend has said he'll paint the walls but nothing has happened.
I feel so resentful of this situation, I hate sharing a room with this kid, I feel like I can't move around incase I make any noise and wake him up if I want to use my phone for anything my boyfriend turns the sound and screen light down, I understand that this child needs to sleep but I feel like a guest in my own bedroom, if his child wakes up crying he puts him in our bed and it makes me soo uncomfortable, I move to the very edge of the bed and lay awake all night.

I hate myself for feeling so resentful of this poor toddler, I don't let anything show infront of him and he's actually rather fond of me but I can't reciprocate, I feel I will always find him to be a nuisance and not an addition,

His dad Is no help, used to not drain the bath out after bathing his son and would just leave all the toys in there, he'd leave his bottles all over the place, in the kids bed, under the bed, wherever it fell, by the time I'd find it it'd have gone off solid milk inside which as my boyfriend works and I don't would be my job to clean out, he'd also leave the kids toys strewn all over the floor and forget to bin nappies. He's picked up on all of this since I've voiced my disconcert.

Not long ago I mentioned him having a child still being an issue for me and he just got angry and told me to 'get over it', he couldn't understand my view point in the slightest. We recently broke up over this situation but got back together on the same day on the condition of him making a few changes re the state of the bedroom, his lack of discipline in areas I feel VERY strongly about - how his child treats my pets, but I feel like this will always remain an issue for me.

My boyfriend regrets becoming a parent soo young and I think he resents it, he doesn't show much interest in playing with the child. He hate the early mornings that come with parenthood an has on a few occasions expected me to get up amuse the child so he can sleep for an extra hour (the kid likes spendin time with me but he's there to spend time with his dad) I have said this and that I don't see why I should have to get up early, it's not my responsibility, he's very easily irritated by the child so even if he gets up and let's me sleep for another hour it doesn't take long before I'm asked to watch the child so he can step outside for a cigarette I de stress before he kills him.

I have said I probably won't want any kids and my boyfriend has said he's happy with just his son, this offends me, I can't help feeling like he was happy to have one with his ex but not with me.

I don't know what to do, I'm putting up with a lot because my boyfriend works and I don't so I feel i ought to be grateful and just go along with this (I have a mental illness and it makes holding down employment difficult, I'm starting to look for work but I'm terrified) but for now he pays the bills.

I just think they'd be better off with somebody who actually likes children, when his child plays up or starts crying I don't think "aww maybe he's tired" or anything remotely sympathetic, I just think I can't wait for him to shut up, and yes I guess I am jealous that I would never be my boyfriends main priority, my ex had a kid so I haven't been somebody's main focus in a relationship since I was 18, I'm sure that must be better than this.

Any advice would be really appreciated.