Van will not accelerate and seems to not be getting gas what would be the problem?

I have a 99 plymouth grand voyager and it is not accelerating and will not run right. It seems to not be getting any gas to it could it be the fuel pump making it run bad.I took it to oreilys and they said something about the gas, but was not for sure. I just started. It ran fine this morning and this afternoon it had a hard start and then it would not accelerate.