First off, welcome to the group! I can relate to you, I'm also an eighteen y/o female and I have lupus. The best advice I can give you is don't jump the gun, you don't know if you have it yet and the only one that can tell you if you do is a rheumatologist. I would make an appointment and express your concern about the possibility of lupus. That way the doctor can run the tests and do the exam and let you know what's actually going on with your body. I know it can be very hard not to worry but try your best to stay positive until you know for sure. Hang in there and I hope you feel better soon
Also if you have any questions feel free to ask!