I feel it coming

I feel so sad and anxious lately. I feel like my change into adulthood it's coming too soon. My mom it's starting to tell me to find a job and help with the pay of the mortgage which I understand cause she's a single mom and she has all the pressure on her. We are three kids in the house and one of them has autism. I am scare of disappointing my mom. I do want to help her with the mortgage and the house expenses but I also want to finish college :/ I'm just 20 and have a lot of things to do. Learn to drive, become a citizen, finish college and help my biological sister economically too. (I'm adopted) this afternoon I was thinking that all my responsibilities are taking me to the point where I just want to kill myself cause I'm scared of being an adult and a disappointment. I know everyone it's expecting the worse from me just because I'm not the biological kid. I'm sorry I just needed to vent.