Hi I am experiencing the same kind of symptoms, with dry mouth, and really bad taste in my mouth, And peeling on the roof of my mouth, and severely chapped lips all of the sudden, after giving oral to my boyfriend as well So I started researching cuz i had the sore throat cold chills and body aches so it scared me cuz this was three days after I had given Oral, and I was worried I had caught something from not protecting myself with him. I looked up what flu bug's were going around, and strep throat is going around but I still don't have piece of mind, And now with my mouth having this awful taste in it and dry mouth, so I looked up toothpaste side effects, because I did recently change my tooth paste to sensitive with whitening, and several people are having the same issues so I just changed my toothpaste to Colgate today.. And I'm going to see my OBGYN to get thoroughly checked for any other issues.. Thought this might help..
Any STD you would have gotten the the mouth you would have gotten when you had sex also and the tests prove you don't have a STD. Actually you would have gotten it from intercourse before you got it from oral sex.
Hate to say this but only thing you can really do is follow up with your Dr or see another Dr.
Doubt to be STD related.