I'm going to assume they weren't sugar free since I know you know to avoid that stuff. I can't say that chocolate anything has ever bothered me before, but I think it can for some people. I seem to recall a bunch of people on here at one point in time saying they will eat chocolate even though they know it will bother them.
Aside from gift chocolates which are hard to resist and improper to refuse, might I suggest, if you have a chocolate additiction, to eat really expensive imported chocolate. My favorite is a Mika bar. It's made in Switzerland, but I know it can be found in the British Isles. Cadbury's chocolates are pretty good--definitely above a Hershey's--but they're still not the best of the best. You can usually find Lindt (Swiss) chocolates at Wal-Mart (I get them at a frou-frou grocery store called The Fresh Market), and then there are the Ferrero Roche chocolates. I got some of them for Valentines--yum, yum. And Godiva, of course, but that's really pushing expensive. Toberlone is also good, but I get annoyed when the carmel bits get stuck in my teeth.
ANYWAYS, the point of the matter is, expensive chocolate is so much richer and better tasting than the cheap chocolate they put on regular candy bars and the like, that a little bit will satisfy you. And if chocolate is going to make you sick, it might as well 1) be good chocolate and 2) require as little as possible to satiate you so you will get as little sick as possible.
Just my chocolate theory.