What testing did he want to do? Did he tell you why he wanted to do those specific tests?
What probiotics are you taking? What antibiotic did you take?
Here's some basic info for you - https://www.healthline.com/health/sticky-poop
Have you tried tracking your diet? When you started this, did you start any other meds than the antibiotic?
There are some good reasons to do the testing, depending on what they are, but maybe you can start with diet since your stool test didn't reveal any blood or infections, etc.