Major anxiety should I go to the ER??

I cooked something on the gas stove last night around 9pm. I thought I had turned it all the way off but the little knob on the stove was still slightly turned to low, so it was on and had no flame. I didn't notice this all night. I went to work today and got home at 5. When I walked in my apartment had a very very strong gas smell. I immediately checked the stove and turned it off. It would have been left like that for about 20 hours. I happened to be on the phone with my dad who told me to call 911 and leave the building, so I did.

Firefighters came and checked it out, the gas company and apartment maintenance all came. They checked the levels and said it was fine but to keep an eye on it. The smell has gone down a bit but I can still smell it even with fans on and windows open. It's now been a few hours and I feel very sick. I feel spacey, nauseous, dizzy, my head is pounding and I feel lightheaded. Maybe it's completely unrelated and I'm just paranoid?? They said it was fine earlier but I am over thinking and worried about sleeping here tonight. Is this worth going to get checked out just incase, should I just leave my apartment tonight, or am I just being paranoid?