Is it too late?  No.  I am USMC reserve who wanted to be a pilot in the Marines but I decided  not pursue a pilot career after I joined.  If you want to be a military pilot, I'd say your best bet is to look at the Airforce.  Why?  Better aircraft.  Bottom line.  If you like old helicopters, you probably have at least 80+% chance of flying them in the Marines.  Very few pilots end up flying fixed wing in the Marine Corps. 

Since you already have a degree you would apply to Airforce OTS as a non rated pilot before 28. If you choose the Navy, I believe you have roughly the same age limitations.  My best advice to you is to try to learn about the actual lifestyles of pilots in both services and go with what you think is best for you.

Check out these other forums.
www.airforceots.com (airforce)
www.airwarriors.com (marine/ navy)

Good Luck