What are some examples of what healthy boundaries look like when it comes to dating someone who lives with an ex?

In my case, they have been involved with in some fashion for over 10 years? I know that this relationship is a very meaningful relationship between the two of them. I like his ex, she’s a really nice person. I hate that I feel insecure when I know they aren’t physical and I believe him 100% that they won’t be. I do. My insecurities I think are just about the nature of their relationship in general still feeling very coupley. I dont know. I’m confused and trying to sort myself out here.

Recently I have been dealing with a messy custody battle with an abusive ex. Having to prep my evidence for court and reliving some of the traumatic experiences I went through is making me feel small and weak and insecure. Reminding me of how worthless and fragile I felt then. Putting me back into a negative headspace.

The last week I’ve noticed myself becoming insecure over the relationship my boyfriend still has with his ex. They live together, share about everything, and are very very close. They talk daily throughout the day, spend one on one time together still, he is still very much her comfort person. They cuddle and watch movies and hangout. None of this bothered me before. But now it does.

As I’ve been going through this stuff, he’s been at my house 4 days a week on average. Giving me the support I need any way that I need it.

I know some of my insecurities are stemming from being triggered by reliving my abusive past as I prep for court, but also maybe some of my insecurities are valid? I’m not sure. I’m trying really really hard here to make sure I separate what is stemming from my past, and what kind of behavior would be realistic for me to be upset about?

I love this man. We’ve been seeing each other for a year now, what started as a purely sexual BDSM Dynamic that has now transitioned into a full blown romantic relationship. I love him deeper than I’ve ever known love could be. He’s very important to me, the most caring and genuine person I have ever known. I feel so safe with him. He is aware I’m struggling with insecurities. I’ve communicated them. He’s being so amazing and patient and willing to hear me out and talk through it.

I just need advice. I’d like to hear about healthy boundaries when it comes to ex’s being involved?