Just for context, he is a (young) doctor and i'm a student nurse. He sometimes calls me by my name but other times he calls me 'sweetheart'. I can't tell if he means it in a nice way or in a condescending way.
The other day, I was just doing my own thing and he came over to ask if i'm okay. I replied yes and then he kept questioning me, saying "Are you sure?", "Really?", "Are you sure?". It made me feel uncomfortable because he made me feel like I was incapable of taking basic observations from a patient, even though I knew I was doing it correctly. Then he said "Okay, sweetheart" and walked away.
Another example is when he held a door open for me and I said "Thank you". He replied "You're welcome, sweetheart". I don't know why he keeps calling me sweetheart. He only seems to be a few years older than me, so it's not like he's an old person who calls all young women "sweetheart" and "darling".
He also tried to embarrass me in front of other colleagues. I get along quite well with the other nurses, some who are male. This doctor called me out in front of everyone on shift that day, saying I should spend "less time flirting with the male nurses". I wasn't even flirting with them- we were just talking and joking like normal friends/colleagues do.
Ugh he is just starting to annoy me but I don't know what to say to him without seeming unprofessional because at the end of the day, I still have to work around him for 12 hours at a time.