pap smears don't routinely test for stds so it is entirely possible they missed it in your first test. Also, it is rare fror asymptomatic chlamydia to suddenly become symptomatic unless we're talking PID symptoms but this does happen.
Cramping, diarrhea, maybe vomiting, a fever, discharge.
If you were actually tested in January (and you need to call and confirm that) then it is most likely a new infection for him, too.
But does it matter? He cheated and got infected with something and you got it. Does it matter if it was 6 months ago or a week ago?
Aj