diet pill questions, is this how they "work"?

So now that Im pregnant I'm cleaning out my medicine cabinet. I look at all the things I cant take, and the things that will expire soon (within a year) and toss them.

As I get to my "weight loss section" I realize something. They all gave me diarrhea. Is that how they work? about day 4 of taking something I get the runs, decide that's not worth it, and stop.

I toss the Stacker, Acai pills, Zantrax 3 (or whatever it is called), Slim Quick, and so many others.

Im not sad at my "loss" and know those things don't work anyway. But is that a normal reaction to all diet pills. is that supposed to happen, or am i just unlucky?

thanks for reading and feeding my cuorosity.