Missed period question!

How soon can you miss your period after conceiving? I was on microgestin (lowest dose of progestin birth control pill) since May. My boyfriend and I have always been very careful with me being on the pill and we always use a condom when we have sex. I decided to get off the pill in late September after some undesired side affects. I got my period at the end of October on schedule, but I did not get my period for November yet. My boyfriend and I are in a long distance relationship so the last time we had sex was six days (nov 21) before I was scheduled to get my period on November 27 and again on November 27 (I still hadn't gotten my period). We were safe and used a condom both times and they did not seem defective. I don't know if my cycle is just irregular because my body is adjusting to not being on the pill, or if I missed my period due to stress. Is it possible to miss a period this early if I have conceived because my period is now a week late? Is it possible that the condom was defective?