I had similar issues with Harley around 14 weeks. I tried EVERYTHING and she just would not move....I never gave up though, we worked on it EVERY day. I think you just have to be consistent and let him know that this is what you expect and don't except anything other. He'll get the hang of it eventually....IF you don't give in. When I was having this problem, I too turned to the great people here on YT. So glad I did....the below post was what really helped me and as I began practicing it day by day, Harley eventually walked and it was the best feeling ever. Pay attention to #3...dogs pick up on your emotions and they can sense everything. I started to leave the driveway with Harley and would picture in my mind arriving at the stop sign at the end of the street. THAT was my purpose...to get to the end of the road. She followed...I think if you stop trying so hard and just expect, really internally expect that he will follow, he will. Harley and I now go on regular walks no problem 
Good luck and keep trying....he'll cave eventually.
1. Short, short leash.
2. Don't let her put the brakes on. Just pull her is she does. Not hard, but firmly.
3.
Walk with a purpose. - this is an IMPORTANT one!
4. If she tries to walk inside your legs, put pressure on the leash and push her out, while saying "no!", or whatever you use (ackkk, etc.).