i was very naughty and now my fate lies in your hands!

[Redskinluver]

I agree with Aurora, and everyone else who said that a spanking is not appropriate in this case, not at this time. Like they say its a matter of rebuilding trust. Or maybe even the relationship is over.
Also, since both you and your bf sound like novices in the scene, I am concerned about the scenarios, they all sound very severe and excessive, you're talking hundreds of licks. A spanking should not be something that causes major physical injury. Perhaps it is your feeling that a severe beating would help purge your guilt.
Maybe if you decide to go ahead with a spanking, maybe a maximum of 100 with the hand on your bare bottom, or up to 50 with the hand and a max of the same number with a hairbrush or CB paddle, or one similar.
Others may have other suggetions for you.
But remember, a spanking is not a "magic bullet" that will cure personal problems.