severe pain at 25 weeks

I will be 25 weeks on Monday. For about the past week, my hips and knees have been hurting me pretty bad and getting worse every day. Two days ago my right knee got bad enough that I put a brace on it to try to relieve some of the pressure while walking. And now today, standing, sitting, laying any way you could possibly imagine, just brings excruciating pain. I tried to walk across the house (small house) to the kitchen and ended up in tears. I can't handle it. Please tell me someone knows what this could be and how I can get relief. I don't know what to do.