AITA for no longer wanting to babysit my baby brother?

I already talked to my cousin about this, but now I feel even worst since I feel like maybe I’m making myself seem like such a victim for no reason??

Anyways to really tell what happened from my point of view and why I decided to do what I do. My mom had recently had a baby late last year, and beginning this year I had offered to babysit him whenever my mom needed. It’s gotten to the point where I take care of him 4 days out of the week, from 7am all the way to 10pm. It’s been getting exhausting and it doesn’t help that the baby is in his teething phase, causing him to become grouchy most of the time. It’s also always a struggle to change him. Overall he’s acting how any 6+ month year old would act.

I don’t know what I expected. I didn’t want to think this will ever happen. It’s gotten to the point I’m literally the one raising her baby for her and it’s just stressful. I had dropped college due to how often I was told to take care of him, since my grades were dropping due to me always paying attention to the baby.

Today I decided it would be best to tell my mom that I could no longer watch her baby, since it was getting overwhelming having to watch him all day. I love my brother so much, and I really don’t want to feel like he’s a chore..

My mom got bothered, and started to give me attitude over it. Now I feel really bad but I know it would be good to put myself first, since I’m barely beginning my adult life?? (I barely turned 18) I just don’t want to have to raise another sibling because of a decision that wasn’t really in my control. I just been so drained.

Now I’m just scared my mom will make me feel worst about it, since I’m the past she would tell me how I wouldn’t make a good mother since I couldn’t handle her baby or that she now won’t be able to make money to provide for us.

I feel terrible to have even tell my mom that I couldn’t anymore since she does so much for me, but I’m losing my mind-