After standing still for 5 minutes or more my heartrate goes to between 120-140. it does the same thing in the shower when i get hot. why, what to do?

Worth more study: It is possible you are dehydrated, anemic, or have "neurocardiogenic" pre-syncope, or less likely, "pots". These are types of autonomic dysfunction. 110/70 is not abnormally low. If you feel light-headed, though, you should see your doctor. Bupropion can reduce the metabolism of adderall, (dextroamphetamine and racemic amphetamine) leading to high heart rate and even risk of seizure.