Backfired

2 days ago I stopped off at the gas station to get some brew.
Returned to my 2002 AWD Chevy Astro Van. Turned her over to start the engine and it backfired pretty good When I attempted it again it took several attemps. when it finally started running there was a loud noise coming from the muffler. And it sounded like it was going to quite. When I put it in drive it did just that. So after a few more attempt's I got it on the road. The performance and hp was awful When I got home about two miles.I got out and popped the hood. It had a very strong scent of un burned fuel. I let it sit over night incase possible flooding took place. Next day same terms. Didn't want to start And when it did run it wanted to kill And the return of strong odor of Un burned fuel. What might be the cause