how does medication help depression?

♡ 𝓚𝓪𝓽𝓻𝓲𝓷𝓪 𝓵𝓸𝓾𝓲𝓼𝓮 ♡
I'm really really depressed, I have an amazing gorgeous baby boy but my circumstances have been unfortunate. I don't even have a house of my own and I am being made to feel unwanted now making me feel uncomfortable. 
My mum basically abused me and my sisters, stole from us and is a bipolar , narcissistic alcoholic. My husband went from a charmer to a narcissist and abuser too.
It feels like everyone I get close with ends up being this horrible person, even my mental husband couldn't love me and I cry about it because I know that if I ever wanted "attention" It would be from me showing pics of his son to him but I don't wanna put my son at risk. I'm just sat here knowing that no one wants me, I've got no friends and I live ever day the same, on repeat. 
I'm technically self harming by punching my leg which is now all swollen, sore to walk on and bruised to high heaven! 
What do I do?
Doctors don't help they are PAID to listen half arsed with you and your problems then give you a tablet which , I've had before, makes you feel emotionless.
What REALLY is there I can do?