Hi all. I apologise but I'm in need of a bit of a rant 
the last few months have been such hard work and now I really feel like I'm struggling to cope with everything. Just before Christmas last year it came out that DH had been messaging an 18 year old co worker and had been sending her dirty photos etc while I was working. This girl took it upon herself to message me on Facebook and send me screenshots of messages and photos between them. Thing that hit the hardest is that he was joking with her what excuses to give me for him being late home for work several nights a week and excuses he used to sneak away to see her. In my eyes they are both as bad and guilty as each other and at the time all I could manage to rely to her was you're welcome to each other. Bearing in mind I worked 25 hours plus overtime every week and cared for our son full time outside my job with no help from DH and also helped few days a week looking after DSD from a previous relationship. He forced me to take the job as he said his wages weren't benign for "us" to survive even though he made no contributions towards anything other than his half of the rent. It ripped me apart. All of this started 3 months after we got married! Her excuse for messaging was she knew he was married but it's just as much his fault as hers and she thought I had a right to know. Then she proceeded to tell me he had blocked her on Facebook so she couldn't message him anymore so she got pissed off and wanted to get back at him for it after leading her on for months. I was devastated. I didn't know what to do other than lose my shit. I asked him why and he said he couldn't answer me and didn't know why.
He has repeatedly defended he won't do it again and he would prove to me he won't make another mistake but when I get insecure about it he gets pissed and says I can never let things go and get over stuff.
Knowing I couldn't leave as I had no family or friends to rely on or even anywhere else to live with DS he said it would be unfair for me to leave him because our son would suffer. Guilt trip I know but I grew up in a single parent household and seen my dad once a week for a few hours and it was horrible. He kept telling me to let it go and get over it and that everybody makes mistakes. I tried my best to get on with it but every time he disappeared with his phone into the bathroom for a half hour or he said he was working late my brain went into overdrive. His response to this was "do you want me to not have a phone to make you feel better". I ended up with severe anxiety and lost my job with the stress of everything and then I got it cast up to me that he was paying for everything himself because I felt sorry for myself and lost my job. I was on sick benefit after GP prescribed me medication and wrong that time ended up paying for gas, electricity and food shopping by myself every week as well as paying for clothes, nappies and shoes for our son. I have never had any help from DH with paying for DS clothes, food, nappies etc since he was born because he uses the excuse that he pays maintenance for his DD from previous even though he's in a good wage. A couple of months went on and we argued because he said I was becoming unbearable to live with because I always complain about how tired I was and nagged him to help out every now and again with DS because I needed some sleep so he threw me and our son out of our house and told me if I couldn't deal with the situation I was to go and left me homeless. I sought help from homeless team with local council who helped me secure a flat through deposit guarantor because I was on a low income and didn't have a massive deposit to pay. A few weeks after I moved in DH begged me to help him as he said he couldn't afford to keep the house we had together running himself and had nowhere to go because his mother wouldn't let him move in. Me being me agreed and he moved in. Things were okay at first and DS was happy to see his dad every day but now it's slipped back to the usual. He sleeps to afternoon most days, even on his days off, doesn't help with DS in any way, complains when I ask him to pitch in towards paying bills every now and then (once a month I ask for him to help pay electricity when it's my skint week) and treating me like a live in maid. Thing is he can be involved when DSD is here and helps etc but not any other time. My dad has recently been admitted to hospital for an op to remove his voicebox after his cancer came back so I'm caring for DS every day all day on my own and visiting dad as much as I can until he can get home.
DH cheated before with his ex (mum of DSD) and 2 girls he had been with before but this was before I was even pregnant with DS and we took time apart after it happened before he asked me back.
I have no contact with bio mum or her side of the family as she was abusive physically and verbally until I left home at 14 so my dad is all I've got.
I'm at an end and don't know what to do anymore