how do i trust my partner

I'd like to know if i will be ever able to trust my partner again, I'm struggling and have been for over two years now.

Maybe im just being paranoid but it really stuffed up my mental health.

I met him in July 13, and it was great.

I am older than him and I was hesitant to start with, as my ex was really bad to me. He knew this.

I worked away three weeks at a time, and he understood my job, we decided to enter into a relationship at the end of august 13.
It was a long distance romance but we travelled to be together.

looked forward to the phone calls and love followed.

He is the nicest happiest person I had ever met.
I decided to move nearer him and he moved in, with me till his house was ready. He had bought and done it up. He wanted me to live with him.
The kiss of death for me was picking up his phone and finding deleted messages from a girl of 19.
He said they were friends, from before he knew me.
I had no reason to doubt him.

So after moving in with him, giving up my family and friends and coming to a new place I find these messages one saying the sex was awesome, another saying where they were meeting that night, after the pub etc.
I looked 8 her fb page and also seen a photo of her and her friend posing in the living room from the Oct 13.
The texts were at the same time, I asked him if he had slept with her, he said no, no no. Wouldn't answer my question, leave the room.

so I asked the girl she said they had been seeing each other before he met me, she has a baby to his ex pal, I think that is why his ex pal doesn't talk to him.
I told him what she said, he said she was a jealous xxx.

I went back to work after time at home for my three weeks and he said he was missing me terrible, and on one occasion he said he was going out with his brother who is friends with this girl.

They used to all hang out together, I wasn't happy as his brother was newly single and wanted my partner out with him drinking.

anyway the truth came out one night in the may 14, that he did sleep with her but not in this house, Internet a great thing, there was photos of her in our bedroom too, before we had moved in, taking photos of our lights and photos of her fully clothed in our bath. Only found these recently now I want the bath out.

It makes my skin crawl the thought of her in my bath.

In the may I confronted him again, it ended badly, and he shoved me when I gave him his character, resulting in me being off my work for 18 months now, and one operation later. He is so sorry for what happened but I blame her as well.

All the lies came out and she is getting on with her life and my partner won't hear about it anymore.
its been hell.

He's had to support me financially since as I can't get benefits and if i could have I think I'd have left, but being at home all the time we ended up so close.

He is a good man but I don't trust him, right at this moment he is at work, he is working on a job where the owner is great friends with the girl he slept with, and the owner is opening the place this weekend and he said there has been lots of people up there helping, I've asked who, he didn't say, but brought up that he knew I was thinking the girl was there.

It has crossed my mind. He thinks the owner doesn't like him, then yesterday said he had been invited up for free drinks and food, I said I thought she didn't like you.

I hate going out with him in town it's a small place and that girl is always out and it ruins my night because I really want to hurt her.
so we hardly go out.

I will be heading back to work soon and I'm already ill thinking that he will be straight out partying with his brother and that bunch of people.

He says I need to get over it, but I'm not.

The girl is a trollop and has a bad name around the town.
I just no that when I'm away he will be out drinking and I think he is a opportunist and would cheat again.

We really do everything together and we are strong in so many other ways.

its just this it won't leave me.

When I was looking on his phoneiI also seen he had called sextet lines and tvx.

He is always wanting sex it's constant and I can't see him

going without. I know this all happened before we were serious but it still hurts.