Hi Aleandre and welcome to Healing Well. I know a little about AS not much. You said they did blood test, did they do a ERS and CRP? There is also another blood test they can do that will show if you have the gene for AS. The test is called HLA-B27 gene. Even if you test positive it does not necessarilym mean you have AS but it can be taken into consideration with other positive testing. Have your dr done any CT's of MRI's to check for inflammation in your joints? As generally hits the spine and sacroliac joints in the beginning. It can affect other parts of your body as the disease progresses. If you cannot get anywhere with the dr you have then get into another dr, don't give up.
Sometimes if the inflammation is mild it will not show up in blood work. Try to get your dr to do further testing with either a CT Scan or an MRI. Its much better to catch AS in the early stages and slow the progressio of the disease down. Good luck...Susie