Azie the comment "no further action" is one of those standard (unhelpful) phrases that the GPs click on from a limited pick list when viewing results or letters. It does not mean that there is nothing further that they can do, but just that on reading that particular result in the huge pile of results and letters that they are working through, (so without your particulars in front of them at that moment) he/she has seen that it has not revealed anything that they need to do immediately such as refer you to a consultant or ask you to come in to see them because they need to discuss something that the result has shown up, or book you for a further blood test etc. These pick list comments are just notes for the secretary or receptionist to take further action on, so as I say, very unhelpful for you as the patient. In my role as a receptionist, I will always explain this to the patient when reading out the doctor's comments. The receptionist you spoke to doesn't seem to have been thinking from your perspective unfortunately. Doctors have to rule out stuff in their diagnosis so these particular tests giving the all clear on that route just means that the doctor now has to have another rethink as where next to look.
So you must go back and say that ok those tests were clear but I am still in a lot of pain so where do we go next and keep pushing for an answer.