Sterlina, I had a similar reaction to eating sugar alcohols about 16 months ago - severe stomach pains that felt like the worst case of indigestion I've ever had. I thought I was having a heart attack at one point it hurt so bad.

Reactions to carbs when you've been LCing are not unusual. Severe reactions are usually a sign that you are allergic to something. Eating excessive carbs can mask these allergies, eating LC and then going back to eating something that sets you off can mean a severe reaction.

It's possible that it's not just 'sugar' but something specific - like lactose or grains (two of the big common ones - the others being nuts, soy, shellfish). Your best (and most obvious) bet is to avoid the 'real things' and perhaps have something LC from the desserts recipe section once in a while (the NY Style Cheesecake is awesome )

Cheers,
Nat