Last month my cycle was irregular. Normally it is about 6-7 days long and always 28 days apart. I had lighter bleeding than usual. The first 3 days seemed normal for the most part then the last few days were barely even worth calling a period. Which is not at all normal for me. Now this month my cycle is 11 days late, today. I'm trying not to get too worked up, but if I am pregnant, would I count back from my last (irregular) cycle or from the last time I had sex?

You count back to the first day of your period. You need to take a HPT using first morning urine to determine if you are pregnant.