Heart Rate and caffiene/energy drinks

I recently purchased a 305 forerunner and Ive been monitoring my heart rate closely. I drink alot of caffeine usually, at least a 24oz monster a day minimum. I went on a group ride monday an hour after consuming a 16oz monster my heart rate sky rcocketed to 188 20 minutes into the ride and i became extremely tired eventually came down to 160-170 for the 1 hour and 40 minutes  remainder of the ride. I layed off caffiene for 2 days did an excellent 2 mile run heart rate never went above 166 same with cycling the day after. I had to go into work early drank a 16oz monster and 2 12oz cups of coffee ran after work and my heart rate was up to 190 felt short of breath extremely tired. Im starting to think the 2 are connected but does anyone have any opinions? im 24, 165lbs 5'11" I read my max heartrate should be 180