15 1/2 weeks, killer knee pains at night

Lizzy

Not so much during the day, and it doesn't matter if I've walked a ton or sat on the sofa all day, but at night my knees are KILLING ME. I toss and turn.

Last night it was so bad I couldn't fall asleep till 3am. I just rolled from side to side with my knees on fire.

Anyone else? What could it be?