Sex+pregnant

Kate • 19. Married. Mama to a little boy 01•22•15. Military wife. CA.
Im 6wks3d pregnant w/ baby #2.. I just had sex with my hubby and i couldnt even continue having sex bc i was having trouble breathing and got really dizzy and shakey.. Does anoyone have any clue of what it could mean? With my first pregnancy,I didn't have this issue til i was 8mths pregnant only bc of how big i was + the baby, so I understood that. But why am i having that issue now? Yes i drink water.. Like alot.. So it can't be   dehydration. Thanks in advance 😊