I need to get something off my chest

I'm in a really rough situation right now, i had to move back with my mom because my fiance cheated on me with my bestfriend. We were together 5 years and have a 3 year old. I was a stay at home mom because of his job, which caused us to move every 3 weeks to every 6 months depending. I have previously delt with anxiety and depression and was on medication but i stopped taking them because of issues with my insurance. Now being at my mom's i always hated it and moved out at 16, but is the only place i had to turn to. My mom isn't a bad parent and i truly believe she has my best interest at heart, but keeps low key putting me down. Just tonight she called me a bad mother because my son cries or throws a tantrum. Like i know she is no longer used to having a small child in the home, but toddlers cry for no reason. She told me that he was crying because i was ignoring him, yet he cried because i told him he couldn't have any soda because it was bedtime. One thing led to another and she said some every hurtful things. I'm a bad mother because I'm young, it was my fault that my fiance cheated on me because of who i chose to be friends with, my son suffers because I'm the mother he has, I'm selfish when i go to the gym while my son is at headstart or when i go to work, I'm putting my mom responsibilities on someone else when i allow my son to visit his father's side of the family, I'm disrespectful when i stand up for myself. I know I'm not perfect, but I'm trying. I'm not allowed to talk to my sister about how i feel because all i do is cause drama. I lost my bestfriend and partner the only people i could truly talk to and now all my flaws are being pointed out on a daily basis. I'm lazy when i stay in bed until i have to pick up my son from school, but i physically cannot get up. I honestly don't think i would be here without my son and i know he needs me and it's selfish to think he would be better off without me, but somedays are just too hard for me. I don't want to sound ungrateful, I'm blessed to have my mom that supports me and took me in when i had no where else to go, but it just hurts..