Get him in a structured class so he can learn confidence thru his training. If you do hire a private trainer, please get one that knows the breed...try to get a good recommendation, and not a barkbuster type trainer.
7 months is the beginning of the dogs independent awareness and they will take 'control' of situations if they feel their handler isn't giving them guidance. Because the dog is still so immature they don't know how to decipher a threat or not...especially if there is some fear based aggression attached to their personality. He probably feels your fear in his behavior. Dogs sense way more than we give them credit for.
I would be careful with his daycare experiences too. How is he there and is he getting some structure or is it all freedom?
Step up your NILIF
and build his confidence thru him knowing you have his world under control so he won't have to feel 'on' all the time.