I drink so much coffee while i'm at work. is this safe?

Depends on amount: Caffeine is a mildly addictive stimulant. Drinking even 3-5 cups of coffee a day is probably safe, unless a person gets stomach aches, jitteriness, palpitations, sleep problems, etc... Decaffeinated coffee is likely safer, with few or none of the undesirable effects seen with caffeine. One should be sure he is not adding too much sugar or fat to his coffee drinks, as that would be quite unhealthy.

Depends: Some people are profoundly affected by caffeine and others are not. I have had patients who cannot sleep after one cup of coffee (esp after noon), or even get bad tremors. While modest use of caffeine (2-3 cups/day) is likely not harmful, higher doses do raise blood pressure and pulse, increase anxiety, cause sleep problems. It is also addicting, causing headache in withdrawal. Taper down to 2-3/d.