I've been with my DP almost 2 years. He's been separated from his exw about 4 years bu they always stayed friends. At the start of our relationship he was still married to exw and didn't see the need to divorce as "it's just a bit of paper". They were still very close - lots of texting conversations through the week, shared a car (it was her car but he had free parking so she parked the car at his place and he used it more often unless she wanted it, for example if she wanted to do something at the weekend she would take it), and met each other weekly to have dinner together and catch-up, or to go on nights out to the pub/bars with her and her DP.
I really struggled with their meet-ups because he had a habit of meeting with her and I would only find out afterwards, and often by accident because I had tried phoning and couldn't get through to him, despite asking him to be transparent and tell me in advance when he was meeting her.
I was very uncomfortable and pressured him to reduce contact and divorce. He has divorced now. It became a bit frosty between them during the divorce, and (slightly before the divorce) because he began to limit contact with her (for example, she had asked him to drive her and her cat to the vets, I was uncomfortable with it, he delayed in agreeing and she took a taxi instead).
The divorce was amicable and very straight forward as they have no DC, no shared property, no shared-finances etc. Things seem to have warmed up again now, they are texting each other to wish each other happy birthday, happy new year, sharing photos of their Christmas dinners with each other, giving each other updates on promotions at work, sharing youtube links to things she knows my DP is interested in. They have a long history (over 20 years together) and I think my DP would be happy to go back to weekly meet-ups with her if I wasn't so upset by this.
I feel like he is still attached to her. I want him to cut contact with her and focus on our relationship and building a relationship with me. I'm worried that even if we marry and have children he will still have a relationship with her. I don't want to be reminded of their long history together and want him to leave his past in the past.