Aggressive border collie

My boyfriend has a 7 year old border collie who is extremely protective and loyal towards him. Overall he is a good dog who is chill and listens most of the time but, in the last few months he has become increasingly aggressive towards me. We have lived together for a year and he used really only growl at me when he was eating and a few times if I jokingly hit my boyfriend or slapped his butt.

Lately though he shows aggressive behaviour towards me almost every day no matter what I am doing. He actually bit me a few weeks ago on the leg, didn’t draw blood or really leave a mark but he put his whole mouth around my thigh as I was talking face to face with my boyfriend. Sometimes if my boyfriend and I are getting ready to leave the house the dog will growl and show his teeth and me, this morning I let him outside and he did the same thing. This has gone way beyond just being protective of food.

Most of the time is he completely fine around me but the aggression is increasing quickly.

I genuinely believe that he will bite me someday and it will leave a mark. I won’t let this dog around my family or kids because I don’t trust him. My boyfriend is mostly blind to this aggressive behaviour, this dog is his baby and he loves him more than anything. My issue is that I feel like he doesn’t believe the aggression means anything. As well, we were talking about the dog biting me with his parents and he said that he doesn’t think he actually bit me.

I am really miserable over this. What should I do?