E.T.
My second son was 5 weeks early. He was only in the NICU for 9 days, but when he was discharged, one of his orders was that I had to take him to physical therapy. He didn't really need it, it is just the standard procedure for premature babies, but it definitely gave me peace of mind. I only had to take him every 3 months, but the PT would show me exercises to do with him to help strengthen his muscles and keep him on track. He ended up only being about a month behind where my older son had been. I'm sure your son is fine, but you could always talk to your pediatrician and see if he would recommend someone for you.