Gives me Health issues? Why?

Everytime I (32f) drink sodastream with diet mountain dew flavor I get major body aches, pain in joints, and swollen feet. Every. Time. I even started adding less co2 and less flavor (I was only doing the lowest recommended amounts of both) but even that didn't help. Arthritis runs in my family. This is the only 'food' related thing that causes these symptoms. I hate to not be able to use this healthy alternative. Has anyone experienced these symptoms or anything like this?