Fuckwhoops is an expression to be used only in situations that are extremely dire. Fuckwhoops is used when you are overcome with emotions of distress as well as realizing that this unfortunate situation you have now found yourself in is your own fault.
Ex. 1: Arielle: The keg was gone when I went to get it.
Kevin: Fuckwhoops I shoulda got it earlier, that's what i get for expecting you to be capable of doin work.
Ex. 2: Arielle: I forgot my keys
Kevin: Fuckwhoops now we're stuck here. That's what I get for letting your bitch ass drive.