Had fever 3 days ago. Woke up 2day w/unusual sore throat and extreme dry mouth. (ive had constipation 4 a while, not sure if related) possible causes?

Dry mouth. dry mouth/sore throat may be interrelated. If the infection (you have a fever) has caused partial airway obstruction you could be treating through mouth rather than nose. See your PCP to determine cause of your fever and appropriate treatment. If fever disappears and you still have dry mouth/sore throat, then see your Dentist or an ENT.
Not dental related. I suggest you see your primary physician.