If you would, I can use your advice

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I got pregnant with my rebound...I'd been with my high school sweet heart for six years and made poor decisions when I broke up with him. The man I got pregnant by ended up trying to kill me 3 months into my pregnancy. I battled depression and trying to be strong enough on my own through my pregnancy and the court hearings for what he did to me, and I lost weight through my second trimester. Now that I've had my son, (who is the most amazing person that I have ever laid eyes on) I had to quit my second job because I hurt my elbows. I have been left in massive debt because of this man (er bills, a truck he convinced me that we needed, and I agreed because he didn't have a vehicle at the time, needed to get to work, and we were engaged). Since I had to leave my second job, I have gained 20lbs. I suspect because I've been so stressed with paying the bills and trying to balance my life as a single mother. I have always been overweight, but this weight has been too much. I can't be battling these self esteem issues when I need to be finding a way to pay off this truck and also afford the car seat that I want for my son (a diono rainier) just as an example. My sister moved in with me, but whenever I tell her i can't eat that because I am trying to get to a point where I am healthy she essentially mocks my efforts.
It gets to the point where I am ready to forget about my personal goals because they conflict with my life in ways that seem to difficult for me to handle. But I dont want to let go of my health, I feel that I would be failing my son if I let myself go.
So I am asking that anybody who is willing to, friend me and hold me accountable! I really need this if I am going to succeed, and I truly want to. I just need some accountability, so that I don't forfeit with the thought that everything else is more important.
I know my happiness directly affects my son, and I want to be the best mother, role model, and support system for him. His father isn't allowed to contact us for 12 years, so I need to be the best and happiest mother that I can be, so I can fill his father's role as well. Ultimately I'd liketo lose 80lbs but my goal for now is 20. Anybody looking for a motivation partner friend me! Help me as best as you can, and I promise I'll do my best to help you too.