Hi Ksong. I had this problem with my neice and nephew and my family, mostly my mom. I just had to sit them down and explain what RA feels like and then explain what it is like to be around children who want to climb on you and kick their legs and stuff. It isn't a big deal to them because they don't hurt constantly. A kick from a 4 year old because they are kids and can't sit still (understandably) is excruciating. You can't recover from it before you get kicked or climbed on again. Enduring that and the chaos is so incredibly fatiguing that you can only take small doses. It is like having the flu that you can't recover from.
It doesn't mean you don't love them. It just means you are sick and need their support and understanding until you can get back in treatment. The 8 year old should be old enough to understand that you are sick and that they need to be gentle and helpful. Are your kids supportive and understanding with your situation?
If you are able to see a doctor and get a valid prescription, some pharmaceutical companies can help you with free meds.
I know you are going through a rough patch. Hopefully your family will be supportive if you speak up.
KT