I am wondering what is missing in your current relationship, and why is it so unstable?

The instability to me speaks to your desires for someone else. Perhaps your current relationship is not the right one for you.

Also, it seems you have a pattern of being attracted to the bad boys -- someone in prison and now, someone who has been locked up for 30 years. Innocent or guilty, he's been locked up for a very long time. Not to mention, you work with him. I am not judging, but this seems like very poor judgement on your behalf. It is also inappropriate to extend relations with this man outside of your work environment. That is also very poor boundaries and poor judgement.

Are you in therapy? I think it would greatly benefit you to see a therapist to talk about your issues. Again, I am not judging, I am just being open and honest about what I see based on your post, and I think you need to evaluate your relationships & behavior more deeply.