I have been taking him out for almost a week now, just short walks in the local wood or up the road to the shops. He is 13 weeks old but small. He seems to be getting less interested and keeps on sitting down and I have to really pull him to make him walk. He is more interested and faster on the way home! Do you think he just needs more time and I am doing everything to quickly, we are only going once a day for maybe half an hour?
The general rule of thumb with puppies is to walk them for 5 minutes per day for each month of age, so your dog at 3 months old should be walked for about 15 minutes each day.
But I doubt that's why he's sitting down - I expect it's because there's a lot to see and take on board - he can't have long had his second jab. The outside world is a bit overwhelming and interesting all at the same time. He also has to get used to the concept of a lead and walking at the end of it. Dogs don't just know what to do when you clip a lead and collar on, they need to learn what you expect. Encouragement and treats will make the world of difference.
You do have the best opportunity at the moment to teach him to walk to heel though - before he learns to pull on the lead!