What's Wrong With Me At The Moment? Sharp Pain/Ache?

It only started about a half hour gao, I was in the car eating a mcflurry (not sure if this has anything to do with it but every detail is helpful right!) and I go tone of those pains thats almost indescribably, it starts around the lower back area and affects your whole abdomen. Anyways, I thought I just needed to change my posture so I sat on my foot, but that didn't change anything. I tried walking for a while but I walked with a bit of a lurch, if I stood upright it would spark up the pain. So now im on my computer and I still feel it. Its right under my sternum, maybe around the stomach area? Up a little maybe? But it feels like an ache and a bit of a sharp pain. I don't know whats going on but it's pretty uncomfortable. How can I fix it? Thanks! :)