First hot yoga class

Amazing! I survived and feel 10 pounds lighter. Actually, just 2 pounds, but I feel great. I found a yoga studio close to my house that specializes in hot yoga and has a 30 day trial period for new members. I read their website before my first class and made sure I drank plenty of water and brought a large towel. I could not believe how much I sweat! I completely soaked through my t-shirt, shorts, underwear, and beach towel. This must have been part of the detox process I have read about. Have you every experienced this detox process? Some of my first thoughts as I was putting my towel down and looking around the room at some of the younger and slimmer bodies--can I survive 90 minutes, will I have to leave the room, will I faint, or should I try my best and lay down if necessary? Have you had these thoughts in class?
At first I could feel the intensity of the heat and humidity and started to sweat. Class started and my mind was racing and I was a bit nervous. After about 5 minutes and several postures I forgot about the people next to me and began to focus on my own body and breathing. This new breathing process called Pranayama is intense and different than my typical breath. The teacher explained pranayama breathing and took several small breaks throughout the class to demonstrate. Lot's of beginners in the class and I felt more relaxed. 60 minutes into the class and we started the floor series. I was ready to stop but told myself to continue at about 50% effort. I was a little sick to my stomach and a little light headed and decided to continue but at a much lighter pace. After all, this was my first hot class and I did not want to ruin my first experience. I'm glad I paced myself as the next 30 minutes was not easy. After about 70 minutes into the class, I took childs pose, and rested while still doing the pranayama breathing. 90 minutes is up, and I'm soaking in sweat, and ready to stay on the ground for the rest of the night. I think the teacher called this corpse pose? Perfect name. I'm dead tired and don't want to move.
Driving home my head hurts from a slight headache and I'm thirsty? Has anyone experienced a headache after Bikram or hot yoga? I thought I drank enough water before class but maybe I need more. Time for a shower and something fruity for dinner.