I’m pretty sure this was on PBS tv  as part of an independant  film series.
It’s  perhaps an hour long, from the mid-90s, before he was cast into Law & Order Special Victims.  He is a  great guy, well-liked, engaged to be married.

He feels compelled to share his deep secret with his fiance’– which is that he is an alien.  She thinks it’s an elaborate prank, then gets angry when he won’t admit to it. so finally he does say it’s a joke.   I think she shows him the door., breaks the engagement.  He then goes to her parents to try to get her back, tells the father the same alien story.
The thing about this is that his elaborate story sounds plausible with the details he provides, and in the end the viewer wonders– what is the truth.

a movie seen on tv, possibly on ‘Lifetime’  approx 2002-2009. I seem to recall Charlize Theron playing the character but don’t see anythng matching in her film list, so that’s a guess

A beautiful  brainy businesswoman has chance meeting at an airport with handsome (of course) businessman,  resulting in a  short fling, which he ends.
I think he was married.  Gets him in big trouble with evidence against him of malicious stalking and physical attacks. Possibly a trial w/ him as defendant.
It turned  out  that although she is brilliant in IQ–she’s also totally delusional, fabricated everything. . .because she  is a highly-functioning schizophrenic.  Ends with her in prison  conversing  with an imaginary woman,  a former friend I think

but she’s delusional, ruins his life.