I don't drink coffee. Really don't like it.
I used not to drink anything with caffeine, then I met my first husband who was a big tea drinker and I switched to drinking like a pot of tea a day, if not more.
Then I decided to cut on caffeine. Now I only have it when I need to stay awake for work or something, and I typically get it from diet soda because they have premade sizes so I don't abuse it as easily.
It is generally agreed that consuming up to 300 mg of caffeine per day is safe. That would be about the amount of caffeine you would get from three cups of coffee.
If coffee is your only source of caffeine, you can have up to three cups of it. Most people though will have something else, like soda or even chocolate (although I guess chocolate has very little caffeine in comparison). You can also get it from medication (when I quit caffeine I got withdrawal headaches, which is normal, but then I realised the meds I took against the headaches had caffeine in them, and I had to switch to a different med). These have small amounts but if you're already on the threshold of what's safe it could be significant.
I also would think that getting it all at once isn't as good as spreading it over the day (like one cup when you get up, one during your break if you get one, and one for lunch).
I should say though that I definitely have heard of people consuming more coffee or caffeine than you do. Doesn't make it better for you, but you're not the only one.