Shower curtain that wont stay put. please help!?

We have an itty bitty bathroom. Literally you sit on the toilet and your knees touch the shower. the shower is 3 feet by 2 feet. the curtain hates us. When we are showering the curtain likes to come in at us making our space smaller. the only way to get it to go back down is to open it up and let air out. I have tried adding extra weight to the bottom and the fan in the ceiling doesn't help at all either. I have never had this problem before. Whats causing it and what can i do so i have more shower space?