Hello. Welcome to HCM.
There can be many causes of amenorrhoea, Most of these have to be ruled in or ruled out depending on age. Commonly, they can be (apart from pregnancy
1. Hormonal imbalance
2. Uncommon infections of geitourinary tract leading to synechiae formation
3. Functional ovarian cysts.
4. Beginning phase of climacteric (menopause
All these need to be ruled out by stepwise investigations. In your case, visit to gynecologist will be helpful. May be you have to undergo blood tests for hormonal levels (LH, FSH, PROLACTIN
) and even hysteroscopic evaluation of uterus and adnexa.
Hope this helps.