What am I doing wrong ?!

Everyday I wake up to work 2-10 my daily commute is and hour and thirty minutes , I'm currently 30 weeks pregnant . I have a 5 year old son while I recently made the hard decision to let him live with his dad due to being homeless , I'm trying to save up I'm trying to be strong and not cry . I recently missed his 5th birthday on the first and my newborn is due nov 9th . I'm trying my hardest to live and save up for an apartment but me being 19 and doing this alone I just cane hold it in anymore . Once a week I just let it out and cry and apologize To my children , I feel like the worst mother every and the worst woman ever . I could never give myself props or even say I'm a good mother because what kind of mother puts her kids thru this ? I'm currently living with my boyfriend mom and sometimes I want to give up , sometimes I want to disappear ..... idk what to do anymore .