Hi Dear ,
Welcome to HCM.
Understanding your concern.
Thanks for your query . It is normal to have sour taste in mouth during 
pregnancy . The most probable reason for sour taste in mouth during pregnancy is hormonal changes . 
For sour taste i would suggest you to suck on mint candy and eat yogurt as it is 
probiotic. This taste is temporary and go away with time in case of pregnancy .
As far as bump behind tongue is concern there could be many reasons like hormonal changes , lack of enough vitamin, weakened immunity and stress . 
So i would suggest you to start taking 
multivitamin supplement under expert advice , eat more citrus fruits, maintain proper 
oral hygiene , do 
betadine mouthwash rinses  and try to keep your stress level low .
 If condition persist or get worse consult your doctor for proper examination and to rule out other cause . 
Hope your concern has been resolved.
Get Well Soon.
Best Wishes,
Dr. Harry Maheshwari