19 weeks pregnant and nearly fainted today.

I work in realestate and i was in training at a house today. We were inside the house standing and I was starting to get very unconfortable. I started sweating and feeling very hot. When i was about to go stand outside to get some air, my office manager told us to go outside where it is cooler. Once we got outside i started feeling extremly bad. I felt weak very hot and started geting a blackout. I also could not hear very well from either ears. Some of my collegues and manager helped me lay down and get some water and gave me air .I had eaten a good breakfast and a good lunch before leaving to my training. I was wondering if anyone has gone thru this and if so what they were told happened. I have a docs appt. in two days and will tell my doc. about that incident. Thank you in advance for your answeres.