I suppose it was probably a case of timing; your relationship was very much on the rocks and this other girl came along at just the right time. I am glad that he has finished with her and you are working on yourself so that in time you can work on your relationship together.
It sounds like you are being very sensible, now, about your illness, even if you haven't been in the past.
Have you been ok today with the Sertraline side effects?