You could definitely be pregnant! However, it would most likely be too early to tell. Lets say you ovulated at the latest of the dates you've given (day 18) you'd be two days past ovulation, or if you O'ed on the 14th day, you'd be 6 days past. It's best to wait until *at least* ten days past to do a test, 14 to be safe. So based on your latest possible ovulation date, I'd wait to test until 6th-9th may to test Goodluck!