Hip/leg/knee pain

I will be 15 weeks on Friday and I am having terrible hip/leg/knee pain at night. I am a teacher and started back to work last week where I’m on my feet all day but it doesn’t bother me during the day. What do you ladies do for this?? I am constantly waking up barely able to turn over bc of how stiff I am. I just got a mattress about a month ago, so it is definitely not that.