Food Poisoning

A
I ate at a weird sushi place on Sunday and then I think I got food poisoning on Monday because I vomited and felt the worst nausea I've ever had. On Tuesday I felt better but not fully, same with this morning but now it's 8 pm and I feel nauseous again. How long does this last?? And why have I been feeling better until right now?? Pls help This is so much worse than the flu :(((