Anyone have any idea what could be causing this?! Been on amoxicillin for almost a week now with no improvement.. it's actually gotten worse. The roof of my mouth hurts sooooooooo bad. They tested me for strep but it was negative so my doc said it must be a sinus infection. But the roof of my mouth wasn't as bad then. Just a side note: I do find it interesting that this happened to me last year in the early spring as well. They thought it was hand foot and mouth disease and it eventually went away on its own. I took Benadryl last night to see if maybe it was like an allergic reaction but no luck. Anyone experienced anything like this? Have I given the antibiotics long enough? What do you think this could be?