Please help ASAP

[evolve35]

Ok, need some advice.
Ran into him in the hallway. He was walking by, I saw him, looked away and said how are you? in a friendly, neighbor-only kind of way, not making eye-contact as I didn't want to engage in actual conversation. He stops to talk anyway, wants to know if I got the letter he brought for me that he had put in my work mailbox. I said yes, then he wanted to know if I had gotten the letter from his lawyer as he had gotten a copy. I told him I didn't know as I haven't checked my mailbox. He said, "OK, no biggie" and walked off as I continued to look elsewhere.

I have been doing so well here at work the past couple of days but this just takes the wind out of my sails. I can't concentrate, feel nauseated.

I am thinking of setting a boundary... maybe matter-of-fact telling him that he has hurt me more than anyone in my life and continues to do so when he talks to me about this at work... could he please not discuss this with me at work.

Is this too much to reveal. Should I just tell him not to talk about this at work? Am I doing too good of a job acting nonchalant? He obviously searches my eyes to see what I am truly feeling. I have been all smiles much of the time in the last couple of days.

Thanks for any input...