my 5 month old is developing really fast, could i be pregnant?

Forgot to add:

Early physical development is a result of muscle strength. Babies can't consciouly "work out" to gain strength faster because they sense a new pregnancy. It happens when it happens. Generally, the only motivating factor in speeding up development is older siblings. Babies want to be able to do the things they see kids close to their size doing. Once they realize they have control over their body (which only happens once the myelin sheaths are formed over the axons, completing nueral pathways and allowing for faster transimition of signals to and from the brain) they can work toward trying to do things they see other kids do. But again, it all depends on the child.