I Am Prescribed 20 Mg Of Adderall To Take 3

I am prescribed 20 mg of adderall to take 3 times a day and I just started it 2 days ago. I did take a months worth of 15 mg er adderall first but my doctor switched me to 20 mg of instant 3 times a day. The first day I took 3 and everything was great except I took the last one too late and had trouble sleeping. Now today I only took 1 20 mg tablet at 10 am and it's 7 30 now. My resting heart rate seems to be about 108 beat per minute all day long. I am prone to anxiety and it was very slow at work today so all I do is think about it. Should I be concerned in the immediate future before I can talk to my doctor on Monday? Today is Thursday and she's out until monday.