Hey there. I know myself how horrible these symptoms can be, but you should know that they are almost always caused by minor issues, if anything in particular at all.
Lightheadedness, nausea and headaches are symptoms of just about anything, including anxiety. It could also be allergies, or a virus, or an ear issue. Lightheadedness itself can cause nausea, as can headaches. A trip to the doctor would be the best way to assure yourself that there is no serious issue, but I think just about everybody on the forums can tell you that they've felt as you do now :)