nausea, dizziness, fanting??? what could it be??

also, this morning.. I was in the shower and i shaved and everything.. and i was almost done.. just rinsing off but i started to feel nausea.. very bad.. and i had to hurry and get out of the shower.. and was feeling dizzy and starting to black out.. i could barely walk. i sat on the toilet and it didn't help.. so i walked to the living room and fell to the ground.. and layed for a few minutes.. i was week but finally started to feel better.. i also had the chills. do you know what this could be??? ( it happened in a similar occurance a week or two previous of this except the last time i was just waking up )