My last period started Mar 8th (I have a 30-day cycle, 30 days between the first day of my period and the first day of the next) it was a few days late. We spent the last week of Mar and first week of April on vacation, so I was figuring my period would be late due to the excitement (my cycle is very sensitive to changes). We stopped using birth control (spermacidal jelly) on the 10th of April (technically I should have been menstruating just before or around that time, but I wasn't). I just went to see my doctor today (Apr. 19th) and had a positive pregnancy test! So how do I figure my due date since my cycle was off this month?