What Causes Dizziness With Sweat?

Hi, we are on vacation & it s really hot. I keep getting dizzy and if I don t stop and sit down, I feel like I m going to faint. I get sweaty, but not dripping, just clammy. When I just keep going, I get very shaky and must sit down before I fall. I take blood pressure meds and think maybe it s getting too low?