I had ghonerrea or however it's spelt & they treat you for both when you have it, when I took the pills my boyfriend & I both had diarrhea that day.. not sure Why it got worse
The symptoms you describe are probably an adverse reaction to the antibiotic. This is common. It is possible that the dose wasn't fully absorbed due to vomiting. Thus, there may still be some of the Chlamydia causing bacteria in your system. So, the infection could come back. However, zithromycin would have significantly reduced the amount of bacteria. So, it is important to wait a few days (if you wish to be retested) because there is a chance of a false negative.
However, it is most-likely an adverse reaction to the antibiotic and the Chlamydia is gone. But if your symptoms become unbearable, or do not resolve themselves within another week, you should go back to the doctor.
This is just my opinion. I'm not a doctor.
Not sure why you posted on the ADHD forum, but .... typically, it takes one to two weeks for the infection to resolve itself (webmd). If you are on multiple doses of zithromycin (with no more bad symptoms), I would expect things to be getting better soon. If that was a single dose of zithromycin, then yes, there is a very good chance it did not get into your system. I am guessing you took it on an empty stomach? You should get back to your doctor as soon as possible if it was a single dose and let them know what happened. Make sure you mention the side effects.
But, even if you are on a multiple dose, I would still let the doctor know what is going on.