Hello, I'm Dr. Deb.
I recently came online and see that your question hasn't been answered. I'm so sorry that you've had to wait for a response, but if you still need assistance, I'd like to help if I can.
I'm a strong believer in the ability of dogs (and cats for that matter) to sense or detect illness or emotional distress in their human companions especially if there's a significant bond present. I think it much less likely that the one dog is detecting pregnancy but I think it quite possible that she is responding/reacting to something going on with you.
But, differentiating between a physical condition or an emotional need may be quite a challenge. If you're going through a lot right now and are feeling anxious or stressed, then she may be trying to let you know that she understands and is trying to comfort you in the only way she knows how.
Dogs have been known to sense when an individual is about to seizure or when blood sugars are too low (or too high); however, I'm not aware of any who specifically detect fibromyalgia issues. This isn't to say that it's not possible, though; I'm just not familiar with any case studies which have reported it.
If you haven't had a physical exam in a while, it might be prudent to visit your physician just to be safe.
I hope this helps although, again, my apologies for the delayed reply. I also hope that she's just trying to comfort you and that there's no underlying health issues. Deb