Sunny, I think you might be overdoing in the exercise area. It's wonderful you can do this but it might be causing more pain because it could be too much. Exercise is wonderful for fibro and helps with the pain...if you don't overdo. In another of your posts you talked about all this exercise equipment that you use. If I used that, they'd be taking me out on a stretcher! 
Gentle exercise is good...things like walking or swimming. If you can do that with no problem, then do some exercise for a short period of time on your equipment. Then see how you feel. If you are worse the next day, then back down a bit on the exercise equipment.
What you have to do is a little trial and error. You try something and see how it affects your pain. If you have no problems, then it's something you can handle. If you want to do more, then work into it gradually and see what happens. You don't want to cause yourself more pain.
Pacing yourself is huge with fibro, too. You can't do things in the same time frame as you could before fibro. I will work a little, stop and rest, and do more. It does get done but not as quickly. If you are a perfectionist like most of us here, you need to give that up. It will drive you bonkers! 
Lastly, don't "plan" on being in pain. At the end of your post you were saying that you know this will happen. You probably are correct but try to avoid that. Instead, don't do things that will give you the extra pain. You definitely don't want to do things that put you in bed. Laying in bed can make things worse!
So, I guess the bottom line is to pace yourself. Start out slowly and slowly work up to what you want to do. I hope this helps!
Sherrine