You have to understand that this is normal puppy behavior. Puppies can play rough and pretend to be "killing" prey. This is the way they're designed to be able to practice and learn how to kill prey for survival. It's an instinct leftover from their wild ancestors. At this stage, it's
all play, "make believe" stuff. He's not mad at you.
Another thing to understand is that dogs don't understand the way we live in our houses. They have to be taught as they mature. They don't know what we mean at first when we say "no" or many of the kinds of communications we use. They don't understand English the way we do, there's no logic or figuring something out in their minds. Their learning happens because there is a condition and response, over and over.
They're guessing for a long time. The ONLY thing that makes them stop guessing is repitition and being reinforced for a behavior over and over. If you try one thing for a while, then try something else for a while, then another thing, of course it isn't going to work because the dog hasn't left the guessing stage and gone into the repitition of a behavior because there hasn't been an ample history of reinforcment. He's confused.
If a dog stares at you while you're eating something, he is not working it all out in his mind logically.... he's not thinking, "gee, if I look hungry enough, maybe I'll get some food." He would lie in a bathtub with his legs crossed and give a heavy sigh if that gave him food. Dogs do what works. If it works to keep nipping you, he will keep nipping you. You need to make it so it doesn't work. You can do this without harsh punishments.
Let's say (to take Jean Donaldson's example
you are living on another plannet with some aliens. They're nice enough to you most of the time. Neither one of you understands the other's language or ways. They go to work and you're left in their home. You watch videos and eat pizza and go to the bathroom in these white porcelin bowls which even flush. It's all great to you. But when they come home, they babble something to you angrily. You have no idea what they mean but you know they are trying to tell you something. When you're finishing up your pizza, they appear to be scolding you but you can't figure out why. When you use the porcelin bowls to go to the bathroom, they babble at you loudly and you still don't know what you've done which is making them act this way. It's absolutely normal for you to eat pizza, go to the bathroom in porcelin bowls and watch videos. It's fun and harmless according to your ways. But little do you know that this is very unacceptable to them. You are guessing what it is that they're trying to tell you, what behavior you're doing that they are babbling and yelling about. You're guessing.
Your puppy is nipping you, but he's also doing other things; he may be vocalizing, wagging his tail, moving his legs, turning his head. Your puppy is guessing which, out of all the behaviors he may be doing is the one you are talking about if he's even thinking that way at all. And these normal puppy behaviors being abnormal to you doesn't even cross your puppy's mind. They're not complex enough to think all that through. Until the puppy has had a long time of consistant, repeated reinforcement, he is still guessing.
Skipping from one tactic to another does not enable him to have a steady supply of reinforcment for a particular behavior. The possibility of communication is lost every time you change tacts.
Remove the reinforcer for his nipping and biting your clothes. The reinforcer is your presence, your clotes, your socializing, your attention, your looking at him, speaking to him, touching him, just being there. As I explained before, remove the payoff for behavior you do not want and be consistant, not for a week or two but for as long as it takes.
If he bites and it hurts, hand him a suitable chew toy as an alternative, get up promptly and leave the area for a few minutes. That's all you have to do. You don't have to scold, yell, say, "no," shove your fingers down his throat. Unwanted behavior will extinguish if the payoff is not there. It won't happen over night, especially with a nipping, rambunctious puppy. It can take months.