I don't have a significat other, but I know when I became so ill I had to move back in with my family, I learned a few things about helping them understand. I need to be vocal, when I need a rest day or just to sit down for a few min, I need to tell them with nice words. When they go do something I can't (hike, run, go to the store, eat food I can't) I have to remember that they aren't doing it to hurt me, but they need to take care of themselves too...I don't know if there's any way to get them to really understand the amount of pain I'm in physically and emotionally, but their support means so much.

Mm mm, he used to ask me to rate the pain from 0 - 10... This way he kind of understands, just remember our pain can be frustrating for him too!
So, after a long time of this, he understand me better... Tell him he must believe you and it's important to you!!!
What helps? Oh, he can help... He can rub your back or spine (my favorite) and he also hugs me often!
Hope this helps ;)