On yaz, (drospirenone and ethinyl estradiol)took antibiotics 28dec and if i finished them 7jan.i had sex last saturday,started a new pack of yaz (drospirenone and ethinyl estradiol) mon 29th,am i still protected?

Sounds like it: It depends on if the antibiotic you take is one that affects birth control or not. You can do a quick google search for the name of the antibiotic and see if it has interactions with oral contraceptives. Most antibiotics do not affect birth control and if I understand correctly you were taking the antibiotics during the placebo days of the pill anyway.