Hi and welcome to Healthcare magic.Thank you for the query.
It can be transmissed if there was only one itercourse and it could be dromant for so many years,even more if left untreated,especially in males. Increased sexual activity may cause clamydica transmission to anither person but it wont aggravate symptoms or infection.Although,it should be cure before next sexual intercourse. It is not advisable to mix antiiotics,you should use only doxicicyclne. But also you should do testing first since there could be combined STD
Wish you good health. Regards