Hives can be from so many things! Try to pay attention to what triggers them. Many of us are sun sensitive - is exposure to UVA or UVB light causing the flares? Sunscreen, covering up, hats all help that.
It could be some allergen - fabrics, detergents, dyes, foods. It is so hard to say! Talk with your doctor and your new rheumy.
If you do have SLE it is likely that you are sun sensitive. You could try, on your own, to religiously use sunblock (SPF 50 or higher), wear long sleeves and slacks, and a hat with a 4" or wider brim.
I wish you the best on your trip to the rheumy - and encourage you to take 2 copies of a list of questions you have - one for the rheumy and one for you. Take the time to get them answered, you deserve to be listened to and given honest answers.
~"I find hope in the darkest of days, and focus in the brightest. I do not judge the universe." (Dalai Lama)