Is it Accurate?

Hello, I am very irregular to where I do not know when I ovulated and my last period was somewhere around mid April. I had taken a cheap Walmart  pregnancy test today and it was negative ( 20 days past intercourse), also I took a First Response test 2 days ago and it was negative too. My question is: Is this test Accurate? and how high of a possibility is it that I am one of those people who do not produce enough hormones to receive a positive reading? Thank you 😊