Yes, there may be a need to adjust or change medication due to a number of physicological causes as one ages, change of diet, live style, etc. Your coreg dosage is quite high compared to mine which 12.5 mg twice a day. You should talk to your doctor...it is not a good idea to be on any medication that is not helpful...
what ken keith said is right. also your body may have built a tolerance to the med and you need to get with your dr to find what works for your body. this happenens alot especially if you have been on a med for long periods of time