This is postural orthostatic tachycardia syndrome.

I collapse once a year without fail. So I thought something was wrong with my body, so I went to the university hospital and got tested and was diagnosed with postural orthostatic tachycardia syndrome? This is the routine I always have when I collapse: my stomach hurts so badly that I collapse and after lying down for about 30 minutes, I feel better. Today was the same. After showering, my stomach hurt so badly that it felt like my appendix had burst that I thought I had a potbelly and went to the bathroom. As soon as I sat down on the toilet, my stomach hurt so bad that my head went blank, I started sweating all over, I couldn't see in front of me, and I lost all strength. After that, my mom helped me to the bed in the bedroom. I don't remember anything from that brief moment (like 15 minutes?). After sitting for 30 minutes, I felt a little better, so I went to the bathroom and my stomach is fine now. But now I have a fever and a headache. I think my stomach hurts and I'm in shock. Is there a treatment for this? It's hard enough to do this once a year.