depression - alone with newborn

♡ 𝓚𝓪𝓽𝓻𝓲𝓷𝓪 𝓵𝓸𝓾𝓲𝓼𝓮 ♡
I don't know where else to turn to. I feel like I'm going crazy! This last year with my husband has been mental, with him emotionally abusing me and me not being able to forget it but I still loved him and let him use me. I did leave him and now I've cut all contact:
Our son ( who I refused to let him see ) is just over 2 weeks old & already in public I have bad anxiety worried he will cry and get everyone's attention.
As  well as that I found out today that my dad of all people thinks I've purposely come back to the UK from my life in America with my husband just to use everyone for money for the baby stuff and free healthcare, which makes no sense as the army funded my health insurance in the US and it's not like me to do anything like that.
So basically my own parents now don't trust me they think I'm going to go back to my husband when I'm not going to.
Then  I'm here raising the baby by myself. Absolutely knackered from doing all the feeds and changes through the night and day, getting 3 hours sleep at the very very most ! 
Yet here I sit with my mind wondering, feeling worthless.
On top of all this my husband is threatening to take full custody of our baby to spite me and I know legally he can't just get that but he is adding to the stress.
I just feel as though I have no importance to anyone, I've let everyone down because I fell in love with a guy I thought I knew who turned out to be a monster yet I'm to blame. I just wish that I could have some insight of what the future holds. As of right now I feel like if something bad happened to me, not many role would be fussed. I'm not important to no one. Apart from my 2 week old son 
What do I do?