I need help!

I'm 17 weeks and 6 days pregnant my first child but second pregnancy. On  Friday (may 20th 2016)  evening like around 6pm I was outside with my neighbor talking about how hot it was and suddenly I felt like passing out. I was fine all day eating watermelon drinking water has this ever happened to y'all? On June 10th I'm having an anatomy scan of my baby don't know if I should call the dr of my incident