Here's the NIH contact information for queries on whether your study qualifies as a clinical trial. It may take a few days, but they will respond.
Office of Science Policy
National Institutes of Health (NIH)
Telephone: 301-496-9838
Email: clinicaltrials.disseminationpolicy@mail.nih.gov
Also, here's a link to the FAQs and case studies to help you decide.
https://grants.nih.gov/policy/clinical-trials/case-studies.htm
https://grants.nih.gov/grants/policy/faq_clinical_trial_definition.htm