did i mess up my engine??

What is your question?

Engine light came on, i ignored it cause last time it was a sensor something simple. we also recently changed the oil. my truck was running hard so i checked all my fluids and no oil. my oil gauges were normal but nothing on dip stick i put one oil in and ran it, it ran fine picked up speed like normal. i travel about 40 miles and noticed the idle was high very high and unusual sorta not catching gear when its suppose to, it starts to worsen its making a raddling noise underneath the truck its made that noise before but i noticed it when we would back up it sounded like something was lose, anyway, its idling while in park its wanting to stall seems like when i turn or slow down it wants to stall but as im driving its catching speed i can go fast its not sluggsh just when im coming to a stop i have to oput it in nutueral and keep my foot on the gas, what is this?