Hello Jimmyt107. I am very sorry to hear this happened to you, but it does happen. Fortunately you were with two Dommes that could more easily bring you down from the cross without causing injury and it sounds like they knew what to do to bring you around quickly.
Usually it's a hydration issue or an overload of adrenaline coupled with a drop in blood sugar from not eating. Eat a light meal before your next session and hydrate well and hopefully it won't be a repeat event. If it does happen again, I would avoid doing activities where you are standing and have your arms raised above your heart. All the best!