When would your next AF be due? Was your last really light one on schedule? Never say never when it comes to pregnancy. I thought there was no way for myself b/c DH and I didn't DTD except 4 days before ovulation but we're expecting a boy in June! The likelihood for you depends on your cycles. If you are pregnant and it just isn't showing up yet, you should be fine acting normal. I maybe wouldn't go off and get drunk off my kiester if there was any suspicion, but even with that, my cousin was smashed at her wedding and gave birth to a healthy boy 7 1/2 months later.
Rae (27), DH (26), Lucas (6/3/12), #2 due in December