@ayatome yeah, this chapter is kinda hard to understand, but in the last panel, you can see the bite mark on his neck, so... In the middle panel, the original Japanese texts said: "Unexpected things do happen", in this case, mean two things: the deaths of the husbands, while crazy, maybe it's just coincidence, and how the master met the doctor. And the reason he said he has the same reason for not getting married, is because the fear of losing them, that's what I guess, my friend told me it has different meaning in the drama, but I can't find any episode for this chapter, so there was a lot of guess work in the final page.
Tl, dr: Yes, they might slept with each other, and the doc bit him, so he "might" lost his memory about it, hence the uncertainty