Marriage troubles

Me and my husband haven't been married a year yet. We have a council house together. We haven't been good for months. But the past month or so it's got worse. He made a new friend that he went fishing with and I knew his family previously and had a bit of trouble from one of them. But they decided to put it in the past. 

Well my husband had been saying for weeks he was gunna find someone else. This lass who is his mates daughter came round coz she was gunna help me with the relationship give me some advice. He brother turned up at the house. We all were going back to her mam and dads house but there wasnt enough room in the car. So what was decided was my husband and her in the car with his son and her daughter and me and her brother walked. When we got there they wernt there we went round hers and they wernt there either. But a lass said he was there last night coz she remembered the car. I was fumming. As I thought he was cheating on me. I went bk round her mother's and explained what had gone on I went for a walk with her brother coz they had came back. When I got back they denied it and said nothing had happened and they took the kids to the beach. But I never got told. When he was at her house the previous night he said he was going to a friends house didnt tell me he was going there. Anyway we got through it abit. 

Then she started coming round more often paying for us all to go the the beach then the next thing was she was staying over and sleeping on the sofa and she would have her child with her to. My husband has been giving her more attention than me more hugs play fighting inappropriately confront of me. Shes been though alot and she can talk to him about anything where she hasn't been able to do that with anyone else. Bear in mind they only knew each other 2 minutes. Anyway I was going in mood and everything coz of it all crying all the time. One time he had taken my keys and my wedding ring off me. And wouldn't let me in the house so I phoned the police. By the time they came I was back in the house. Just before the police had gone they went out for a meal with the kids all dressed up but i didnt know where they were going at this point. 

Then he asked if we could have a 3sum. She said no coz she wasnt into lasses so what was agreed that he would have sex with her then me. I only did it to make him happy. Then a few days later we both did things with him together then we all did things together. Then one night after he wanted us both to sleep in the bed with him in the middle cuddling him. Then it started that she was in the bed every night. And her child cot was at the bottom of the bed. I have started to sleep on the sofa coz he dosent sleep in the middle anymore. He gives her cuddles to keep her warm coz shes got something that makes her really cold. I never got anything off him. So this has been going on for about a month. She pretty much moved in. She helps with food and everything else we need shes always buying him stuff shes helping out with his son. And I just feel like a nanny. I feel like they are married and I am the sidehore. I have been moaning and been in moods I haven't been treating him right I have been talking to him like shit he says I am selfcented and all the other shit. And the reason it carrys on is coz I am not changing my ways. 

Can someone please help me out here. Dose anyone think i am in the wrong or do u think I have brought it on myself?

Should I leave him and go back home to my dads.