Communication and living with chronic illness is a whole field of its own. My strategy has always been to not talk about it too much, but I see how this often causes misunderstandings. Having taught my friends my pain scale helps quite a lot, but I also had to find out how we could learn to understand each other.
If someone asks how I'm doing and I say "fine", chances are my pain is on level 5, and it's costing most of my energy just to function physically, sit, stand and walk. Above 5, I'm not fine anymore I'm "uhm... ok, I guess" and probably acting quite distracted, as I'm actually trying to find a way to get home and try to calm the coming flare.
Now with the people who are closest to me, I've found it best to make sure we speak the same language. Slamming the kitchen cupboards might mean "I'm hurting, I'm tired and I need a hug!!!" in my language, but it probably means "Stay away!" in my friend's language. Either I adapt my communication to their understanding or I take the time needed to teach them what the words and actions mean to me. A common base for communication between loved ones makes everything else work so much better!