Weight or Arthritis?

So my mom keeps telling me to get checked for rheumatoid arthritis as she has it and it's hereditary.
I've usually thought that my aches and pains were really just weight related, and age related, and being sedentary related etc.

But for the past two days, I'm having a lot of trouble going up and down the stairs, I'm really stiff and sore. I just soaked in a really hot bath and it's a lot better. But I'm beginning to wonder. It's so bizarre and out of the blue.

And I've LOST weight.

It's going to piss me off, if I have AR, I tell you what.