Hi, and thanks for your medical question on eHealth forum!
At only 29 years of age, it is not normal to go without a period for months. If you skip periods at all for months at a time, then conditions such as stress and anxiety, malnutrition, depression, overexercising, sudden weight loss or gain (obesity), thyroid disorders and hormonal imbalance due to polycystic ovarian syndrome (PCOS) should be looked into.
If this gynecologist is not taking it seriously, then consult another one. If taking vitamin supplements helped earlier, then it is possible that you have poor diet intake. You can take these and see. If it does not help, seek another opinion. Hope this helps. Take care!