Hi M.,
I don't know if this will help or not but my son, the third child, was a large baby and had a mom, dad and two sisters to do everything for him, so he didn't really do anything until about 9 months. He didn't roll over, crawl, scoot, move. He just smiled, ate and passed gas :o) At 10 months, he began to roll over and crawl, at 11 months, he began to walk and at 12 months, he began running! He was just a late bloomer. I always put him on the floor for tummy time etc, but he just wanted to do things at his own pace. He is no longer a big baby but we all still laugh at his "laziness" to move when he was a baby. I, would, however encourage you to talk things over with your pediatrician just to make sure that everything is good but each child is different. Our oldest was crawling at 5-6 months but took forever to begin to walk (she walked at 13-14 months). Kids move at their own pace. The milestones are guidelines for parents. I am sure that your baby is fine, just maybe a late bloomer.