My blood work came back normal!, so why haven't my period come on in 3 months? Plus im not pregnant. Doc please voice your opinion. Helpp!

Many things possible. A lot depends on your age, weight, stress level & activity level. Also, how long you've had your period & what a "normal" period is for you. Being underweight or very strenuous exercise can cause missed periods. Be sure to see an ob/gyn dr (if you have not already) for a full check up & possibly other tests in addition to blood work (prolactin) that you may need to help find the cause.
Missed periods. Missed periods can be due to illness, trauma, stress, peri-menopause, and hormonal imbalance from thyroid, high prolactin levels, low Progesterone states. Your doctor will run further test to see what can be the problem.