Constipated at 38 weeks?!

I don't know what is going on. When I hit 36 weeks I was extra "loose" thinking my body was prepping for labor and now I am so constipated! I drink a gallon of water a day and have been snacking on lots of fruit but nothing I happening. It's been like this for a couple days now and it is so out of the norm for me. Any other mommas having this issue this late in the game??