We went through the exact same thing! My son was referred for OT/PT at his public preschool and then we followed up with private summer services. Private evaluation and services were covered by our health insurance -- we just paid office visits copays which still add up but it wasn't super expensive.
Things that we noticed -- inability to jump from the ground or off a step, pedal, or alternate feet on stairs -- if these are all true you are probably looking at a gross motor delay. It is probably not a big deal but the earlier you deal with it the less frustrating it will be for him and the easier to deal with as he won't have ingrained habits from compensating. I wish we had started sooner because while my son can do all of those things now it was much harder to "retrain" him to do them the right way. I also found that my son was so advanced in other areas (reading at age three, etc) that he easily gave up at anything physical because it was hard for him and he was not used to having to work at something. Make it fun and don't let him give up too easily. My son can jump and pedal now but he still won't jump off things with two feet -- getting out of the car he basically sits on the floor of the car and steps down one foot at a time where other kids would just hop out.
Things that worked best for him -- a mini trampoline with a handle, horseback riding with an occupational therapist, for pedaling we got him a tandem attachment for my husband's bike so he could feel what it should feel like, sit-ups and other doctor recommended exercises to strengthen his core muscles, making little obstacle courses in the backyard that required jumping and other activities that were tricky for him, etc.
By the way, this is not at all uncommon even though you start noticing what other kids can do and feel like your kid is the only one who can't -- I was amazed how many moms I talked to with the same concern.
Good luck!