yup. thats what i was thinking it could be.I doubt that it is your motor. Just off hand, sounds like bad gas, some kind of fueling problem. It may be a problem with the electrical or computer, one user had very strange running when he had a bad batter and they had to replace several parts.
I'm sure you'll sort it out, don't worry.
bad gas is a possibility but a problem with the fuel system is what i think it could be. i don't come by bad gas a lot.
Try staying with the same gas station company for a good week or two just to make sure it's not bad gas.