Hi. Chronic pain is difficult for those who do not experience to understand. What I do with my doc is bring a list of my most recent symptoms and how it is specifically affecting what I do each day. I am very specific such as: The joint pain in my hands has reduced my ability to type on the computer. Rather than 1 hour per day, it's down to 1/2 per day I am able to continue. Etc, etc. Make notes of your pain, when you are feeling it and any other factors that may be exacerbating it. A journal is a great thing to keep track of how you are doing to show your doctor.
It is hard to explain to loved ones how it affects you without first, freaking them out, and second, leaving them with a feeling of helplessness.
I would recommend looking up the Spoon Theory on www.butyoudontlooksick.com - a very smart woman wrote down this theory for a friend who didn't understand how she had a ration her energy each day depending on the amount of pain she was in. It gave her friend a way to relate to how she was feeling.
Also, maybe assemble a short document that outlines the conditions, symptoms and what to watch for or danger signs. You want them informed but not too scared. You can maybe write a quick narrative about how it makes you feel, how is affects you physically and mentally and specifically things that your loved ones could to to help! That will give them some guidance.
I always make sure they understand if I am unable to participate in an event of some sort, it is not personal. It is simply I am feeling poorly and don't have the energy reserves. Try to give them something to relate to and give them some links to sources they can look up on their own as well.
Without them hearing about it and how it affects you, they will never understand. Good luck and I hope you are hanging in there.