Real-event OCD after losing my dad

Hi everyone. I’m new here and joining because my life has been shattered by grief and OCD, and I’m really not in a good place. I’ve lived with OCD for a long time without ever having a formal diagnosis or treatment. For most of my life it came in waves and I was still able to function well. I had a career I loved, wonderful friends, and I cared deeply for my family. From the outside things looked normal. I never imagined it could collide with something real in such a catastrophic way. My elderly dad developed a blood cancer that affects the bones and plasma, and I became very involved in his care because I loved him more than anything. Early on a medication was discussed after diagnosis, but I became extremely frightened of the side effects listed. My OCD latched onto that fear and I hesitated for months. Eventually the doctor agreed to a watch-and-wait approach after I asked if that was appropriate. The language in appointments was often vague and the word “stable” was used a lot, which reassured the part of my mind that wanted to believe things were okay for the moment. Looking back now, I can see how much my OCD and fear were influencing my thinking, but at the time I lacked the insight to recognise it. My dad eventually passed away, and since then my mind has been trapped in relentless guilt and “what if” loops. I replay decisions constantly and feel like my untreated OCD collided with his illness in the worst possible way. After he passed, I learned much more about the disease, prognosis, treatment etc and that even in the elderly some people can live for years with treatment, which has made the guilt even harder to carry. People tell me to give myself grace and that I made decisions with the information I had at the time and with good intentions. Right now that feels incredibly difficult because I realise it was my brain hijacked. If I struggled with OCD before, I feel much more severely unwell now that it is layered with PTSD and trauma. Losing him is devastating, and the guilt and regret layered on top of that has been overwhelming. I’m sharing this because I’m trying to understand how OCD can attach itself to grief, caregiving, and medical decisions. Has anyone here experienced something similar? I’m sorry if this post is triggering for anyone. I’m just trying to make sense of something that feels impossible to carry alone. It really feels like the most horrific example of OCD.