Hi

Not sue how old your dog is or how long you have had him.

Sounds to me like he is leader of the pack and wanting to protect you
You need to make sure you are the leader.

Teach him to watch you
Get his favourite tit bit
whenever you can say watch me, I used to do it when the tv commercials were on loll
When he looks at you reward him
When you go for a walk continue this especially when another dog is coming towards you, do not tell him off he is not doing wrrong just protecting you
You have to let him know your the boss and not to have any worries
Good luck it will take time but keep at it