general rant; am I being taken advantage of?

This is a long post!
I've done a few anon post regarding this topic but I've never put the full story. This is going to be the full story in detail, probably just to make myself feel better and let it out. I will read the comments (if there are any) but just to let out my feelings will make me feel a huge sense of relief. 
I am feeling resentment towards my mother, a lot. Perhaps it's pregnancy hormones, or maybe this is really how I feel. But it's getting to the point where I can't bear to be around her - which is really difficult for me to admit to. 
Many people have told me she takes advantage of me and I've always let it slide because she is my mother and I would do anything for my family but lately I have to agree. 
We recently moved in together due to the break down of relationships between us and our partners, and for financial reasons we couldn't afford to live separately as rents etc are too high around this area for our wages. Basically even if either of us wanted to we couldn't move out. I am older now and have been living independently from my parents for several years so at first it was difficult to adjust, especially when it came to finances. My mother wants me to pay half of everything which I have never thought to be fair - and I have told her this - because she earns more than me and in the house we are living in she has my brother who is under 18 and eats like a horse and basically doesn't understand the cost of anything. I have always felt that it would be fairer if I was paying 1/3 but whatever, I always let it go because family. Before we moved in together into this 3 bedroom house I told my mum that I was pregnant and there would be a baby on the way, she accepted this and was very excited. But still expects me to pay half of everything even when the baby is here - I may just add my brother will have a bedroom, my baby will not. (Not to mention all the food that I'm paying for that neither myself or my baby will ever get to see).
Her car needed repairs so out of our joint savings she used 1000 for the car which I was fine with, but some of that money is really mine and I thought we would be using that money for something joint for example a deposit on a bigger house for when the baby is here. But I let her use it. 
Then there is the question of the dogs. She told me she was "thinking" about getting a dog. Meaning one dog. I told her I didn't like the idea as the baby would be on the way and it would be difficult with a puppy running about. No more was said on the matter, until one day we've got not one but TWO puppies. She hasn't house trained the puppies and one was so aggressive to me last night that she drew blood. I am worried about the safety of my baby and I think it was really selfish of her to get the puppies when I had said I didn't want them. They're peeing and pooing all over the house, the carpets are definitely going to need to be replaced, I actually feel I am getting breathing problems due to the smell of the soaked in urine. It's just hell. Don't get me wrong I'm not anti-dogs but to have two puppies and a baby is going to be a nightmare.
Any time I have tried to mention any of these matters (and believe me there are more of them than what I've written) it turns into world war 3 and I just can't deal with this stress. 
I wish I could move out but being abandoned by the baby's father has left me financially crippled and I have nobody else to help me apart from my mum. 
Guess I just need to get used to it. 

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