When did I get pregnant?!

Jennifer
Okay, so my last period was on March 31st. My husband and I have been working crazy hours so we only had sex 3 times last month. I was set to ovulate (according to my app) starting on the 15th of April. We had sex on the 8th, 12th, and 27th. I was thinking I got pregnant on the 12th (sounds logical due to when my ovulation was supposed to happen) BUT I tested on the 27th of April and got a negative result, then on the 3rd of May I got a positive. With my daughter I didn't get a positive until 5 weeks 3 days. I am confused about when I conceived...any thoughts? Thanks!