By choosing not to use equipment that may help you to control your dog on walks, he is suffering, and so are you.
If a prong will help, get one.
Other hints:
It takes 2 to pull. A dog cannot pull on a loose leash.
Carry food rewards, and each time the dog is at your left side, reward him.
teach him in your house off leash to "get back" when you ask him. stand with the dog between you and a barrier such as your cabinets, put a piece of food on the dogs nose, move backwards, and help him to go with you. It takes a little time and patience, but you can do it.
at the same time, teach the dog a command for heel position. I use the word "Place".
when you walk the dog on leash, NEVER allow him to get a tight lead. No more pulling allowed, neither for the dog OR you.
If the dog starts to get out ahead of you, do one of 2 things:
Either say NOTHING, make an about face, and head in the other direction. when the dog catches up to your left side, praise and reward him.
OR TUG him back towards you. This should be a smooth pulling motion, not a sharp motion as you would give a correction. Pull the dog back as close as you can get him to heel position, and then immediately drop a big loop of slack in the lead.
Each time the dog gets out ahead of you, do one of these 2 things.
Each time he is close to your left side, praise and reward.
I also would recommend you take some sort of training class with the dog, so much of training is equipment and technique, and technique is impossible to demonstrate here, even with photos.
Good luck!