I am not sure how much is to much. I do know that my midwife suggested taking up to 5000 mg a day with no more than 1000 an hour. I think that is just because your body can only absorb so much at a time. I also have a cold right now, so I know how much it sucks! I hope you get feeling better soon!
Midwife and herbalist Aviva Romm cautions in The Natural Pregnancy Book (pp. 54-55): "During pregnancy the daily dosage [of vitamin C] should not exceed 2000mg, as it can lead to miscarriage in early pregnancy, and can cause a vitamin C dependency in the baby which can lead to scurvy in the newborn."
In acute situations you can take more for a short time, but for routine consumption I try to stick to 500mg in supplements and at least a couple of vitamin C rich foods per day. When I'm feeling run down I up it to 1000mg in supplements.