poor idle

[4seasons69]

when I start my car it usually never just starts right up I usually have to crank her over a few times and give it some gas to get her started. after my car starts it idles like crap. it will idle right around where it is supposed to and then will drop like it wants to die. a few other things when my car is idling the low oil pressure light will come on and off. if it is on and I hit the gas a little it will immediately turn off. but it is never on when I am driving. any help will be greatly appreciated. thanks