I can only recommend two other things. Chamomile tea and melatonin. Both are natural and should have no effect on your heart rate what so ever.. Use these in conjunction with good sleep hygiene and it should offer some relief.
Benadryl made your heart race? Was it just plain Benedryl or a benedryl D. I haven't heard of that side effect of Benedryl.. it is an antihistamine not a stimulant.. you have me curious.. I need to dig in my pharmacological database. Here we go.... less frequent or rare side effects with azatadine, cetirizine, clemastine, cyproheptadine, desloratadine, dexchlorpheniramine,
diphenhydramine, or loratadine
Fast or irregular heartbeat; fever; abdominal or stomach pain; burning; chills; clay-colored stools or dark urine; cough; diarrhea; difficulty swallowing; dizziness; fast heartbeat; fever; headache; hives; itching; prickly sensations; puffiness or swelling of the eyelids or around the eyes, face, lips or tongue; redness of skin; seizures; shortness of breath; skin rash; swelling; tightness in chest; tingling; unusual tiredness or weakness; wheezing
There you go. Not common, but it does happen. Now I know. Thanks for that tidbit.

MG