Telling my mom

Ever since I've found out that I was pregnant I've been stressing on the fact that I have to tell my mom. My mom recently just got back into school to be an LVN so now she's working part time and is more stressed than ever. In January she will be going 5 days a week to school and will not be working therefore having to rely on one parent for our necessities and the house payments. Money will be tight. My mom had me when she was 17 but found out she was pregnant when she was 16. I am 16. She has been so stressed and occupied. She's constantly studying and still manages to go to work on a few hours of sleep. I feel like breaking this news that I'm pregnant will throw her off completely. Knowing that she's going back to school to give us a better future. I've failed her miserably and I know she will resent me for it. I just feel so alone and I hate looking at her with this heavy weight on my shoulders knowing I ruined everything.