Feeling Faint in OB Surgery Clinical

I had my first OR observation today. a c-section of twins. It was amazing. I was doing great, totally into what the Dr. and nurses were doing. I was fine though the birth and the suturing of the uterus but as the Dr. put everything back in I felt hot, sweaty, pins and needle and a need to use the restroom RIGHT THEN, I never felt ill but I felt faint and a need to go. After I did so I cooled back down and felt fine, scrubbed back in and returned to the OR with no further issues. I'm mad as hell with myself for having to leave the OR.The nurse I was shadowing was cool and tried to reassured me.
I did everything my professor told us, ate breakfast, had a cup of coffee and OJ about 2 hours prior to clinical, might not have had enough sleep but other then that I thought I was doing everything right to avoid fainting or passing out. I have another OR day for med-surg. in a month, what can I do to prevent this from happening again? Any suggestions would help.