Do I have the flu?

I think I have the stomach flu because Im am going #2 like every 10 or 20 minutes. I feel like throwing up at all times its really bad and my stomach is killing me. I also can even look at food without almost vomiting.

Anyway I was wondering the cause of it. Ive only changed 3 things since its happend.
1. I got some new vitamins that expire 04/08 and I took one yesterday and today I woke up feeling like this.

2. Im taking just the normal GNC weight gainer which I switched to yesterday. I usually take MRP and stuff like this but this happened right after so IdK

and 3. I went swimming yesterday morning and was forced to walk around in the ice cold while wet for about 30 minutes.

Thanks in advance for the help I just feel terrible and hope to find out why/ how can I make this pain go away