It could be a treatment failure. Did they give you different medication this time?
The only other thing is that if your partner is getting false negatives. I'm surprised that she hasn't been re-infected if you are still infected.
Hi you were given azithromycin (zithromax) first I would have thought since this is a single 1g dose in your case taken in four 250mg pills. This is generally very effective for treating chlamydia but does have a very low percentage failure rate. For sure though, the second course of doxycyline (two 100mg pills a day for a week) would have treated the chlamydia. False positives are very very rare so I would have thought you were positive if the test reported as such (and given that you had symptoms). It is possible that your girlfriend just didn't manage to catch it off you. But, what you need to do is go back to the clinic, together, and get tested one more time to ensure the doxy has treated you and that she absolutely is clear of infection or else you're just going to be playing chlamydia ping pong with each other. I am pretty sure the test will come back negative for you this time though.
I went in for an annual and it came back positive for chlamydia. I had a test done the year before when I was pregnant and everything was normal. I have been with the same partner for 4 years. My partner says he was never with anyone else. Neither of us had any symptoms at all. We both went in for treatment to be on the safe side and a swab was done on him. They never called us back with his results. In the meantime I went to another clinic the next week and my test came back negative. We called the clinic we were first tested at and his results were negative. We both have our doubts about why mine came back positive while his is negative. How could this be? It is causing problems for our relationship.