I Gave Blood This Afternoon And A Couple Hours Later

I gave blood this afternoon and a couple hours later I was home cooking dinner and I started pouring sweat, dizziness, diarrhea so I finally laid down and still pouring sweat. Laid around for a bit and then started freezing to death. Took a short nap thinking I was feeling better, got up and started sweating again and diarrhea. What could it be ?