And another welcome to you, mjones! The more the merrier!
Lucky, another couple thoughts to add to the good ideas Julia had...was the 4 pound week when you started out? Sometimes a lot of the initial loss is water weight and the pounds drop more quickly. Secondly, if it's during "that time of the month," that could also be a culprit...it is for me, about 3 pounds worth.
I wish it were an exact science, but it's not

.
Like Quinn said, we'll be jumping on over to the regular 5 - 15 pound thread; people often stop checking this one after Tuesday, which is our check in day. Look forward to chatting with you over there!
P.S. thanks Julia for being the first person ever to use the word "skinny" with respect to me. Tell that to my thunder thighs! Although I will freely admit to struggling with body perception and satisfaction...but hey! For the first time in my life I am happy with every part of my body except one