I think I bought bad gas.

I own a 98 S70 and on Saturday I filled up at the cheapest station I could find. On Sunday my car kept trying to stall out while I was driving around town- in 3rd gear, not slowing, and the car was sputtering. About 5 blocks from home it stalled out and I was able to restart it and get home safely. I typically bike during the week so today I decided to try and crank the car to see if I could get to the gas station to put some nice pricey gas in and while letting her warm up for a couple of minutes she died. Haven't been able to crank since. I have about 16 gallons of this gas in there and I'm thinking that's what it is considering that I haven't been experiencing any other problems prior to the fill up. Any thoughts? Could it be the fuel pump? The check engine light hasn't come on (except when it stalls and all the lights come on). Should I try putting some good gas in or just take it to the shop?
Thank you!

 

maybe dump a little octane booster in first and see if that helps