Any clue what it could be?

The past few days I feel very nauseous but I'm still able to eat. This morning out of nowhere I threw up. For the past hour I've been having pain in my lower back. It's now in my lower back and my lower stomach. My period ended about a week ago. Any clue what this might be? I can't afford to go to the doctor and I would have to take off work to go. Just needing some ideas