We adopted Bella at about 3 and a half months, and she weighed 23 lbs. She is about 18 months old now, and weighs 73 lbs. I have no idea what she is mixed with, so there's no way to what "size" she should be... Do you have any pictures? Shots start as soon as you bring them home. Parvo is a very deadly, highly contagious disease and can spread like a wild fire. Go ahead and make him an appointment to get him in as soon as you can, and don't take him anywhere where he might come into contact with any other dogs until after he has gotten all his puppy shots. Around here, it's a series of 3 shots.