Boyfriend doesn't understand lupus

I have lupus. I have tried many times to talk to my boyfriend about it, but it seems to go in one ear and out the other. Because of his job, we only get to see each other on the weekends and he wants to be on the go 24/7. On Saturday, I had a yard sale and he helped me, after that, we were off to the mall, then a festival. By then I was dragging. Then he stops by lowes(hes crazy over that store), I was so exhausted I went in the bathroom and cried on the phone to my mom. How can I get him to understand what I'm dealing with? I don't want to sound like a baby. Sorry for the mini rant, just had to vent for a few.