Feeling drunk while pregnant

I just woke up this morning and got out of bed and nearly fell into the wall. I started walking down the hallway and couldn't walk in a straight line and had to hold onto the wall just to make it to the bathroom. I feel so drunk! I'm 25 weeks pregnant and obviously haven't been drinking. This is the 3rd time in 2 weeks that this has happened... has anyone else experienced this? Is this just normal? This is my 3rd child and this is new to me.