Have a 3 months old pup. Going out for a walk is fine, he walks either beside or behind me and I keep the leash short. I walk at a brisk pace so it gives him little time to sniff around and be distracted. But when walking back, he starts to walk in front of me and pull on the leash. I have tried stopping and starting, and keeping the leash short as possible so he is next to me. He doesn’t pull when I stop and stand still but as soon as I start walking he pulls. Anyone has any suggestions?