Hi Dana,
You are not being stupid. Having this type of attention from a dentist and then not being able to have it addressed quickly is frustrating, frightening, and stressful.
Have you spoken with an oncologist or your general practitioner about the whitish patch? It might ease your mind to talk to one of them about the biopsy time frame. Your GP may be able to give you some expeditious alternatives to having the oral surgeon do the biopsy. Is this oral surgeon the only one to whom your dentist refers? I would suggest talking to your general practitioner as soon as you can.
Please take a deep breath and try to relax. Try to remember that a biopsy is the only method of diagnosing cancer accurately. If there is nothing you can do but wait for the biopsy to take place on July 19, then try to accept that time frame. It will allow you to let go of the stress a bit and possibly ease your mind.
Sandy