Ate mixed greens that smelled off, food poisoning?

They expire on the 9th and looked perfectly fine but smelled pungent. I ate from the box two days ago and I didn’t notice a smell. I’m poor so I stupidly decided to wash and eat it anyway otherwise I wouldn’t have a lunch. Only a few bite of it tasted off. I ate it almost four hours ago but felt nauseous 40 min after eating it. How long does it take to know if it gave you food poisoning? I have a lot of medical conditions so throwing up gives me severe anxiety. Any advice?