See thats it right there. He never lets there be any slack in the leash right now. I have tried stopping and resuming and he immediately pulls so hard his breathing is super loud because he is choking himself. He is a hyper dog and about 4 to 5 mths. old. He is already 28 lbs. but he is strong! If this helps at all he is a pointer breed.
One thing that all dogs/pups have in common is they have to have something to pull against. People with this problem are often holding their dog with a tight leash, even when the dog isn't pulling. Therefore it becomes a habit with both the dog and the handler. It also desensitizes both to the tight leash.
What is the most rewarding thing? For most dogs it is going for the walk!! (although this can be an exception where pups are concerned at first.)
If you have your pup on your left (doesn't matter) hold the end of the leash in your opposite hand, loop the leash once around your wrist, and have the leash come up the back of the hand between the thumb and the fingers, close your hand. Have some rewards in a pocket (loose pocket, tight jeans just don't work lol) on the same side the dog/pup is on. Start with your pup beside you, sitting is easier but standing will also work if they don't know how to sit. Give your pup all that leash, if the pup moves out of position before being asked, GENTLY bring them back to position. Note: No pulling hard, no yanking and no jerking. I teach this position first, while they remain in that position they will get their meal or rewards. Note: If I have to bring the pup/dog back into position, I don't NOT reward, this would be rewarding for leaving the position in the first place so its a win/win situation for the animal.
Once the pup/dog knows this position (you can train this in the house to start, then move to outside), begin to move forward, take one or two steps and if the pup is still in position reward, if they forge ahead gently bring them back and start again. I use the hand closest to the dog, to control the extra leash, but hold it very loose in my hand and I also reward with the same hand.
If you reward with the opposite hand it teaches the pup to move to the front of us, trying to get across for those rewards by meeting the hand.
I use a clicker, but marking the behaviour you want with a Yes! also works. You also have to in the beginning give a high rate of rewards, but that is faded as the pup learns how to walk on a loose leash.
This is very important: Do not move forward at anytime with a tight leash. Also asking them to wait in a sit at the door when going outside on leash for the walk while you go first also works very nicely.
There are also some great games for teaching a recall at meal time, focus games like Watch Me.
I NEVER use a prong or choke chain, always a flat wide collar and a 6 ft leash.
And I never, do the turn the other way sharply, I have had much better results (100% and with comfirmed adult pullers, including a 2 Irish Wolf Hounds that weigh 150+ lbs) and faster results as well.