Tmi, how do pheromones work

Amber
Fiancé was rubbing my back and out of nowhere went crazy saying I smelled good and keeps smelling my crotch cause it's like a pheromone out of nowhere. Why is this happening out of nowhere. 
FYI I just finished what I think is implantation bleeding I'm not sure. It was a pale pink brownish color. Would that have anything to do with it. 
Never in my life has this happened and I'm 29 lol 
Omg he keeps smelling me going crazy. Lol this is weird I need answers  lol