So for a month my heart rate when i woke up was 110, 112?

So for a month my heart rate when i woke up was 110, 112. and it would stay that fast during the day, maybe more if i was stressed.
NOW
just two days ago, weirdly. my resting heart rate changed.
it is now 88bpm when i wake up and stays that way unless i make it go up by pumping my adrenaline and it goes back to 104. Otherwise it stays at that 88, 98 phase.
why would it just change like that?
im going crazy but i dont know what changed my heart rate. i havent changed anything? im not on any meds for my hyperthyroidism. why would my heart rate change just like that?

Age: 22
Female
Medications: cymbalta