Dry mouth can be caused by a number of things from medications, to systemic problems, even heavy drinking. If the lump has been there for more than 2 weeks, it would be a very good idea to have it evaluated.
I would suggest finding an oral pathologist. Often they are associated with dental schools and as such would not charge much if going through the school program. Other than that, oral surgeons usually have lots of experience with lumps and bumps. They may also be able to find a link to your dry mouth. Once you have a cause, you can go to a general dentist to get some preventive help (dry mouth eventually causes multiple dental problems).
One product you might try until then for your dry mouth is Biotene or Oasis rinses, which act as a saliva substitute.
It's not actually dry, just feels dry. I can feel that there is still saliva with my finger, but I feel like I have a mouth full of hair or cotton. This only happens for about 10 seconds at a time and then goes away. It is definitely not the same as dry mouth or "cotton-mouth" cause by drugs. This does not happen while drinking or taking drugs... certain drugs, and drinking (not simultaneously), actually suppress this sensation.
It's just a sensation of dryness, not actually a lack of saliva. Hard to describe, but I react to it like I would to a severe pain, but it doesn't hurt. I cringe and freeze up. It's horrid, as the feeling of slamming a finger in a car door, but without the pain, and in my mouth. I would rather squeeze Bott Fly larvae out of my face than feel this!
Does anyone feel me here? There must be somebody, somewhere, that has experienced something like this.............dry mouth, but not dry - - - horrid and freakish feeling!?!?
Assuming your past medical history is non-contributory. Your presentations are known as dysesthesia, in which condition peripheral or central nerve dysfunction is implicated. You mentioned that certain drugs can suppress dysesthesia, if these drugs are antidepressants or anticonvulsants, neural dysfunction is likely to be a significant factor. Seeing a neurologist or orofacial pain specialist is advised.