Has anyone had this problem ?

Get a new doctor ASAP. Your PCP is a waste of breath. While some people do initially gain back a few pounds (within the first few years) IF they either lost too much, or reversed to their bad eating habits, the incidence of permanent weight loss in weight loss surgery patients is over 80%, compared to that of 8% for those who opted for diet/exercise only.

You don't need to have a PCP that is a specialist in WLS, but you definitely need someone who is supportive of your decisions and who is willing to treat you for any and all issues that you may have, be they WLS related or not, and that includes vitamin deficiency.