Suggest Treatment For Throbbing Back Pain

I am a 22 year old female. I felt fine this morning, but earlier today I walked around my office and then sat back in my chair. All of a sudden I got a throbbing pain in my left lower back. I put a heating pad on it and it didn't really make a difference. I took an advil, but then realized I ate it on an empty stomach. I quickly ate some yogurt, but still felt nauseous. I tried to eat chicken noodle soup for lunch but it just made me feel more nauseous. I eventually threw up in the bathroom, probably from taking advil on an empty stomach. I finally took the heating pad off because it was making feel like I had to pee. I went home and tried to sleep it off, but had to keep going to the bathroom because I thought I had to pee. I'm now trying to eat toast that way I can take some meds and not get sick. Where do you think this pain is coming from and will the ibuprofen I'm going to take make a difference?