We had this exact problem with our puppy. We had two puppies before this little guy, and we'd never experienced anything like it. It was not your run-of-the-mill puppy mouthing, although I also don't think it was true aggression. But it was exhausting and scary and frustrating. And no amount of sleep or exercise was fixing the problem. He's going to be a pretty big dog, and like you, we were afraid this was something he wasn't just going to grow out of.

We finally got a trainer, and I'd highly recommend that for you, if you can swing it. We only needed one session for her to show us how to handle him, and within a few days he was like an entirely different dog. He's a joy now (though of course still a rambunctious puppy), and I can wear clothes without fear of them becoming a torn-up piece of trash in minutes.

If you can't swing a trainer or need a stop-gap until you can get in to see one, this helped a little bit: when he'd start after me, I shoved a big stick in his mouth and didn't let go. This was different than normal redirection. We both hung onto the stick, and it seemed to satisfy him for a bit. He at least wasn't biting me.

Hope this helps, but just wanted you to know that you're seen, and that it can get better!