My car had no oil in it. I went and got the oil changed, and it was running better .I filled the gas tank up and then all of a sudden the engine light started blinking and it did not have power ,like to accelerate and acts rumbly or shaky.
Don't drive it like that! Flashing CEL is a "misfire", and can cause damage.
Regardless of what happened with the oil, a flashing check engine light (CEL) almost always means there is a problem with a cylinder firing (spark is not igniting the fuel). This also explains the hesitation, and lack of power. This is bad because the unburned fuel can travel through the exhaust and burn inside the catalytic converter, which is then expensive to replace.
In a typical 4 cylinder engine, the car can idle, and even produce some power if 1 or 2 of the cylinders are not firing. At idle, it might even sound normal.
I doubt this is caused by the oil level in your car, but I guess it's possible. Last time this happened to me one of the "coils" was out, so two cylinders were not firing. Note that it could also be something as simple as a spark plug wire that was knocked loose.
Checking the oil level
Just to make sure you're doing it correctly, turn the car off, parked on a level surface and let it sit for 5-10 minutes. Pull out the dip-stick, wipe it off, and put it completely back in (don't even look at it, the reading will be wrong). Pull it back out and carefully check the level.
Also, if there is no oil on the dipsitck, it means the car is probably 2 or more quarts low, but it doesn't mean that there is absolutely no oil in the car. It's not good, but it doesn't mean there was damage because the car was "out of oil". If the oil light never started to flash, you're probably fine as far as engine lubrication goes.