Always fast heart rate although my bp is always 120/80 but hr is always in the 105-120 range. what could be wrong with me?

Many reasons: This problem has a sizable differential diagnosis, which includes hyperthyroidism, caffeine or stimulant use, anxiety disorder, the list goes on. See an endocrinologist or cardiologist and get some bloodwork done to see if there is a physiologic reason for this

No way to know: Probable mild-mod sinus tachycardia. Are you dehydrated? Drinking too much caffeine? Anemic? Profoundly sleep deprived? Obese? Hard to know without getting more details, an exam, requisite blood work, and a baseline ECG. It's worth a trip to the doc's. S/he may want to get an ECG.

Tachycardia: need more clinicals: age, comorbidities, exercise status, blood work if any. For ex anemia, thyroid dz, sedentary lifestyle, excessive caffeine intake, CAD, stress are causes of tahcycardia. You will need blood test, a holter, echocardiogram and maybe an ETT to bring out any arrhythmias (abn rhythms)

Would first see: if hr is low when asleep or if always high and regular. Psychological causes would be very limited in when they occur. Then, what meds/other conditions inc drugs of abuse and caffeine intake. cannot say in your particular case, and would need more info in any case.