Well I'd say it could be two things.
What sort of creatine are you using? for exapmle is it one with lots of dextrose?
or are you using normal mono and adding it to grape juice or water? you get my drift like is it a mixed/matrix type? or is it plain.
And also yeah the steam room maybe the cause.
Why I ask about the creatine is, some people can not tolerate high amounts of dextrose and all that of the sort, they may get sugar high's and low's, I know myself if I have to much sugar like dextrose or fruit juice sugars like grape juice I get light headed.
Let us know.