I have a low heart rate around 45 BPM with chest pains are there any activities I shouldn't do?

Cardiologist. If 45 BPM is not your usual heart rate and you're now having chest pains, the main activity you need to do right now is go to an er for emergency evaluation. If this is a chronic state for you, you need to ask your cardiologist about your exercise tolerance. This can be assessed, and depending on your clinical status some form of cardiac rehabilitation may help you. Good luck.