Test + for clamydia, partner tested negative both treated. tested 6 was later i'm + again and he's negative. only sexual partner. how is this posible ?

A few possibilities: Chlamydia self cures, usually in a few weeks; he may have had it but now cleared. Urine tests in men miss up to 10% of infections. Maybe you had it from a past partner, current partner lucky and didn't catch it. If treated w/ azithromycin, it fails 2-5% of the time (1 chance in 20 to 50). You both should be re-treated, preferably with doxycycline this time. That will take care of it for sure.