I finished a 7 day course of doxycycline for chlamydia. 07/10-07/16 and had no sexual intercourse.. is it possible that the infection is gone and is it safe to have sex again?

The infection was gone by the time you completed treatment. You can safely have sex with no possibility of transmitting chlamydia.

Although the probability of the "infection being gone" is high, as chlamydia is generally sensitive to tetracycline, to be safe , another culture which is negative would ensure non-communication of the chlamydia with sexual activity.