Is this normal for a heartbeat?

For the past 4 or 5 months, because of my severe anxiety, I've had a regular heartbeat of 90+. Sometimes it would peak over 100 when I was overtly stressed. But last night, and maybe for the past couple of days, it's been steady at around 65-75. Why is it dropping? Could it be that my anxiety is subsiding? Or could it be something worse like Bradycardia or whatever? I used to exercise a lot but now I just walk every where I go. I'm 20 years old and attend College.