I've never heard of slim sticks so just looked them up. My first thought was "why would you need them if you're doing the SW plan?"
They claim to stave off hunger pangs - SW allows you so much free food that you have no need to feel hungry, just eat as much as you want from the free food list.
My second thought was that if they "work" you, is it such a good idea to take these if you've already increased your fruit and veg intake? I used to have problems "going" until I started SW and now, because of the amount of veg I eat with meals and fruit that I snack on between meals, that is now very much a thing of the past.
My third thought was "OMG!!!!!!!! Look at the price of them!!! Scan Bran is so much cheaper and probably does the same job!"
If they are making you so ill, then my advice would be to lay off them for a while to let your system get back to normal and try increasing your fruit & veg intake.
Edit to add - Sorry to sound like I'm sounding off at you, I really don't wanna have a go at you hun - its just my opinion so feel free to ignore me if you want to.