Struggling with ROCD in a complicated relationship (married partner, living with ex, constant uncertainty)

TL;DR I (early 20s F) have been in a 2-year relationship with a woman (mid-30s) who is still legally married, lives with her ex, and has a highly complicated shared life structure with them. The relationship has been emotionally intense, largely hidden, and unstable, and has significantly affected my mental health, contributing to OCD and severe depression. I also have OCD that worsens relationship uncertainty, and we’ve had repeated breakups and reconciliations. I’m now trying to figure out if this relationship is realistically sustainable or if I’m stuck in something that can’t work. Long version Throwaway account for privacy reasons. I’m looking for outside perspective on a complicated relationship situation. I (early 20s, female) have been in a relationship for about two years with my partner (mid-30s, female). We met online and became close quickly, and started dating shortly after. At the time I met her, my mental health was relatively stable. After entering this relationship, my mental health changed significantly. I developed severe anxiety patterns and was later diagnosed with OCD. My symptoms are strongly centered around relationship uncertainty, trust, and fear of abandonment. I also feel the emotional instability in this situation contributed to one of the most difficult periods of my life, including episodes of severe depression. From early on, the situation around her living and relationship status was complex and not fully clear to me. I was told she still lives with her ex due to ongoing commitments. Over time, I discovered additional details gradually, including that they are still legally married. Their situation is complicated: they still live together, remain legally married, and have ongoing shared responsibilities and family ties. While they are no longer romantically or sexually involved (as I understand it), their lives are still deeply interconnected for financial, legal, and personal reasons. There is a significant age gap between us, which I feel has also contributed to differences in expectations and understanding of relationship structures. I have never met her ex or her family due to the complexity of the situation and emotional boundaries. People around her are not directly told about our relationship, but most likely infer it. It is generally not openly discussed, mainly because she is afraid of how it could affect her marriage and existing commitments. Her ex, as far as I know, has been generally supportive of our situation. Because of this, our relationship has mostly existed in a private and somewhat hidden form. I do not visit her home and have avoided situations where my role would be unclear. Over time, this situation has created significant emotional strain for me. My OCD and anxiety are strongly tied to relationship uncertainty, leading to intrusive thoughts, doubt, and reassurance-seeking cycles. I am currently receiving help for my mental health and actively trying to manage this. At the same time, my partner has had her own mental health struggles, especially early in the relationship, including trust and control-related issues that affected communication. Combined with my own worsening anxiety, this has created a cycle where both of us have been impacted by each other’s mental health. There has also been a repeated cycle of breakups and reconciliations, often triggered by my anxiety spirals and inability to cope, followed by reconnection. This pattern has become emotionally exhausting for both of us. We are currently not in contact after a recent breakup, as she has said the cycle is no longer sustainable. At this point, I’m trying to understand the situation from an outside perspective and separate anxiety-driven thoughts from realistic concerns about the relationship structure itself. Does this kind of relationship structure realistically work in a healthy long-term way, or is the ongoing instability and breakup cycle itself a sign that it isn’t sustainable regardless of feelings? And how do I distinguish OCD-driven anxiety from valid concerns about the situation?