My partner of 17 years had an affair nearly 3 years ago now, I am still in such a lot of pain, I thought it would have cleared a bit more by now.

we had planned a wedding which was to take place this summer, but was cancelled. we had venue problems and onto the third venue we were driving home when he brought up an old female friend, (who he visited whilst he had walked out on us to have his affair.) I just saw red became overwhelmed by emotion got out the car, slammed the door and went into our home, an evening of heavy arguing ensued.

when we got up in the morning he called me a drunk and unfit mother, when he went to work I packed the children up and went away for 3 days, during that time I sent text saying it was over I wanted the maintained sorted out etc, on his part he phoned my parents as he said he would in the morning to tell them of my behaviour, and ended up effectively slaging me off to my family. so I come home, to 3 days of abuse, he calls the wedding off, saying I need to sort myself out, but denies that he did this.

that was july, we have now spent the entire weekend arguing because we went into a shop close to his work and the young store girl shouted hi XXX and he shouted Hi xxx back. im exhausted need to get it off my chest and any thoughts would be great.

Welcome to MB.

Do you have children together? If so, how many and their ages?

we have three children together 7,9 & 16

You should read the book "Buyers, Renters, and Freeloaders". It will help you understand the dynamics of the relationship you are in. At present, you are both renters. If you were to get married, you would still both be renters. So, just getting married is unlikely to change your relationship all that much. That is not to understate the importance of getting married. If you want you relationship to continue, you should get married. But that will not be enough, because you need to both become committed buyers. The book will tell you how to do that.

Here.
Buyers, Renters and Freeloaders