Dont worry vit D toxicity won't increase heart rate much. It mayb some other reason.
Vit d toxicity cause increase in
calcium levels. Abdomen pain, stones in
kidney, irritability n other features of high calcium.
So better get vit d3 levels if u r taking high dose of d3.
Take medicines for GASTRITIS.
N take ECG if high heart rate is still high n chest pain persists.
Meet a doctor if symptoms persists.