I have been taking birth control for over a year now. However, I had an ear infection over XMAS and was perscribed penicillin (antiobiotic) that may have affected my because. I was on the ab's from dec 29th - jan 4th. I had my last period on Jan 6th. I then had sex the following week or so without use of a condom, however, he was unaware my BC may not be working so we agreed to pull out before ejaculation. I am 98% positive that this did happen, I didn't feel anything and I would imagine I would have if he did indeed ejaculate? (I am not sure, because I have always used condoms before so am not sure what it would be like.) I ended my next pack of pills the past Saturday, and normally I would start my period on Wednesday morning, however, it is now 730 on the Wednesday night and I have still not started, not even a little.
Should I be worried? Or is it maybe just due to the time frames I took my pill? (took one a day late, and 2 more of the pack an hour or two later than normal time).

PLEASE HELP!!

Penicillin should not affect your birth control but to be safe use a condom

The pull out method, meaning the man pulls out just before he ejaculates is NOT a reliable form of birth control.
Sperm can still travel in the pre-fluids before he ejaculates.

No birth control is 100% effective and yes, antibiotics can mess with birth control pills and missing pills or taking them late can throw them out of whack as well.

Only time will tell... your period could be late due to actual pregnancy or just stress from worrying about being pregnant.
If you miss your NEXT period take a home pregnancy test.

Take a pregnancy test, it could just be off a little, don't freak out yet.

Some anti biotics like tetracycline can effect your birth control but not usually penicillian

Okay.. you are suppose to start your period on the 3rd/4th day of sugar pills right? This is my 4th day. I am always on time because of my birth control, that is why I am worried. Are the possibilities of pregnancy high for this situation? I haven't been stressed before, haven't even though about the possbility, but now I am very worried.