Pain in lower left side

Hi guys. So yesterday when I was at school I had some pain in my lower left side. It was going from side to side but mainly in the left side. I also had a fever of 99.1 and it went up to 99.6 within a couple of minutes. It was pretty sharp and severe so I went home. When I got home I felt a little better. It went away for awhile and now I don't really feel anything but when I woke up I'm having some pain again but this time it's a little farther up still on left side. And it hurts worse to walk too. What could this be? Thanks