I drive a 2003 Dodge Caravan sport

I drive a 2003 dodge caravan sport. The check engine light has been on for about a year now, but there wasnt any thing apparently wrong. Resetting the batt. Turned it off only to have it come back on in a few days. Now, hoever, there is a strange knocking sound whenever I begin to accelerate and the check engine light begins flashing. I don't even have to be going fast. We've changed spark plugs and gotten an oil change. The comp. Said cylinder 1 misfire but mechanic sAid all looked good. HELP PLEASE! We don't have much money so we can't afford a bunch of trial and error.