Paladin Build Advice

Hey! I’m a returning player to dnd and I’m pretty out of practice, plus I was already a sort of high beginner low intermediate experience player before, so I don’t recall too much about how to play and build characters yet. Got a campaign coming up and I’m rebuilding an old character in a different setting, but I don’t really know what the best way to go about it is. He’s a doctor essentially, a poison dragonborne who makes antidotes and whatnot with his knowledge and tries to help people in his very chaotic and broken city. He doesn’t have any specific God but I figure he probably will have one as a paladin, but I’m not really sure what oath to go with. I want him to be useful of course, but I don’t mind trading a thing or two to suit him flavor wise better. He’s not *just* a healer because this city is really rough, and he’s a big intimidating guy who sometimes has to fight to scrounge up herbs and medical supplies for his practice to help others, and he has to be tough to make it here, so he does need to be decently strong. 
Does anyone have advice for a good build for a dragonborne that’s still strong but thematically appropriate for someone whose job is to be a doctor in a Gotham-esc city? We’re going to start at level 6 and the dm is a fan of homebrew and alternative contents so the range is any sort of subclasses/oaths I could reasonably get access to to build him. 

Are definitely bent on a paladin?   There is a monk subclass that can be used as a doctor.

https://www.dndbeyond.com/classes/2190880-monk#WarriorofMercy

I suppose I could change the class, but I do sort of want to keep as a paladin. It’s familiar and I feel like thematically it works well with what I’d like to achieve. 

keep it a paladin.  I was not sure how tied you were.  Having come back after a long time out, I did not know about new subclasses (to me.).