What could be the cause of petechiae and bloody noses?

My 14 y/o son has always had bloody noses off and on throughout the years. Some take awhile to stop. Pediatricians always told me keep nose moist with vaseline and use humidifier. Now my some has petichiae (small covering the top of both feet and around ankles). Looks like cayenne pepper sprinkles. I always notices a little, but didn't think anything. It got worse over the years, so took him to peds. to have a look. He told me it's petechiae and need to do blood tests given history of nosebleeds. First round of tests showed blood count slightly low, platelets normal. He called a hematologist. Hematologist told peds to run a Von Willebrand test. It came back a little off. Went to hematologist, he asked if my son scratches his feet. Yes, sometimes, but not often. He did another round of tests to re-check the first tests. It came back prolonged PTT, but platelets ok. He said clotting factor was fine, so why abnormal PTT? He said could be interfering substances, or enzymes. Said he doesn't need to see him anymore...not a bleeding issue. He still has petechiae on his feet (not scratching), and just had a massive bloody nose. I don't understand. If I follow up with the pediatrician, what's next? My son has had several surgeries in the past with no bleeding problems. I had heavy menstrual cycles. Could they be missing something? I don't want to put my son through more blood tests, but???