I have low blood pressure 60/90 and fatigue no matter if i walk, eat, rest. but my heart rate is good. what else should i check as i am so worried?

Depends: That blood pressure reading alone, without symptoms, is normal for a female your age. Symptoms such as dizziness, fainting, lightheadedness, could result from low blood pressure. Fatigue can too, although it's more difficult to ascertaining a cause/effect relationship.

See below: 60/90 is not a blood pressure. The bottom number cannot be greater than the top number. Your pressure is probably 90/60. This can be normal in a 28 year old woman.