It is possible that you got it from the "5 day ago guy" although it's not likely if you used a condom correctly. The test can detect it in it's early stages, but usually it takes about 2 weeks.
Again, it could have been in September as well. Again, not likely if you used a condom correctly.
Remember, you can get Chlamydia via oral (or anal) sex as well. If there was any sexual contact there is the possibility of transmission.
In the end I think your hypothesis is valid. He got it from "her" and then you got it from him.
Regardless, make sure everyone knows and gets treated.
Chlamydia infection can be passed easily through sexual intercourse. This disease can recur easily. You'd better take the medicine that can eradicate this disease. The herbal medicine named . Pill can help you. It can eradicate chlamydia infection and doesn't have any side effects. .. I hope it can help you.