Try not to feel bad, some of us have come by this knowledge by making the same mistakes ourselves
It
is very confusing, there is a lot of conflicting information out there, and what works for one dog or one breed won't necessarily work for another.
You have your puppies best interest at heart or you wouldn't have come on COL
Just try some gentler, non confrontational methods; keep in mind that he is just a baby and has loads to learn (and you too!), and that he will go through lots of phases, some of which may reeeeeally test your patience
but all of which are
temporary and not necessarily a sign that you have a monster in training. Just keep in mind that it will all eventually be outgrown and you will have a dog who is a joy to live with
If you do a search on puppy biting/mouthing/aggression you'll find loads of good tips. Again, what works for one dog won't necessarily work for the next, give something that makes sense to you a chance and be consistent, but if you don't start seeing results, try something else.
And don't forget, baby steps for both of you; baby steps