It may or may not be too late for the builder to pay your real estate broker/agent's commission, but you can definitely still hire one and pay them out of your pocket. There are many things that builders don't always tell buyers because the sales rep/builders are worried about their best interests, not necessarily yours. And remember...the sales rep gets their paycheck from the builder so they're loyal to the builder.
I've helped many a buyers purchase new construction homes in Loudoun County and am currently working with two buyers who are under contract to buy new homes in the area. I would be happy to speak with you to see if/how I can help as well and about what value I can add to the process. Feel free to contact me at your convenience. My contact information is below.
Real Estate Consultant/REALTOR(r)