OK, I was just worried that you based it on symptoms rather than a test.
Do not worry about continuing the trinessa while you did not know you were pregnant. Studies have not really found anything harmful to the fetus in the pill. As long as you just stopped when you found out.
It does not sound like your period in August was a real period. It might just have been some implantation spotting. I suppose that this will be one of that cases where an ultra sound scan will have to be used to determine the age.
If your august period was indeed not a real period, then you conceived around the 20th of July. If the August period was indeed a real period, then you most likely conceived around the 16th of August.
If you have heavy cramping, see a health care provider as soon as possible.
Best of luck!!