20 year old with a 40 year old lifestyle

So I know it is pointless asking this, but am I the only 20 year old around that has to take care of all their younger brothers needs. What I mean is that I am the second mom in the family. It is overwhelming. I have a lot of responsibility. I am a full time student, a full time worker at a restaurant and a full time mom with no kids. I fall into depression easily. I am seriously fragile and I am sick and tired. If I over sleep on a weekend. My mom throws a fit because I didn't clean the house. Don't get me wrong my mom has a lot on her plate. She has a 7 year old with diabetes and a very strict husband. Well my point is that since she's tired all the time, I should be too. Well she's mentally tired, and I am both physically and mentally tired. I try to enjoy my time out on weekends but she makes it impossible. I really didn't live my teen years to the fullest because I had too many worries. It makes me sick how much I am not appreciated. I don't want any of you guys to think that my mom doesn't do anything. She does errons and shit. But put some of her weight on me, plus school, plus work. It's terrible. I know when I get older that I will be on the same boat but that's okay because I'll be older and that's how it should be. But I am 20, living a 40 year olds lifestyle. I hate it. I want to be free and not have to worry about whether my mom will be back in time so she can give my brother his insulin shot.