Hard conversations

I'm having a very hard time living with my mom lately. I am always running around and picking up kids for her and it's a 15 minute drive into town, I pay for 90% of my own things, yet I never have any freedom. It's always oh where are you going, whos there, when will you be back,can you pick up so and so on your way home, can you get groceries etc. I am about to be moving out to university and I find myself not being able to make plans for myself. Two weeks ago I asked my mom to order me contacts because she wanted to change clinics or something, and now as I'm trying to go skiing this weekend I now will not be able to because she could not do one thing for me, whereas 3/4 of my time is spent doing things for her.  My mother got mad at me today because I only told my dad I had tutoring and was going to a hockey game, and when I dropped off my friends sweater after my mother was LIVID because I didn't tell her I was stopping for 10 minutes. I feel as though I need to bring with us with her because if I don't have any freedom now, how am I going to be able to figure it out in university but I am unsure the best way to bring it up without sounding rude. I love my mother but not havin any freedom and responsibility for my own self is killing me.