My period hasn't been on in 3 months and I've taken 2 pregnancy test and a blood test. Can you tell me what can be going on?

Please see GYN. Reasons for missed/late periods: low body weight, obesity, marked weight ^ or v, over-exercise, endurance athletics, breast-feeding, ^ stress, illness, eating disorders (bulimia or anorexia), anovulatory cycle (no egg released), travel, hormone irregularities, drug use, meds (i.e., birth control) or medical problems. #1 reason is pregnancy.
Hormone imbalance. You should see your dr and get some bloodwork to see if you are low in thyroid hormone or what is the state of your estrogen and progesterone.