Week 3 Slump- HELP!

LissaP26

This is the middle of week 3 back on MFP again- I've lost a total of 25 pounds since Sept, with 13 of those being since Jan 3rd. The problem is, now that I'm well into week #3, the loss has drastically slowed and when I get on the scale it's frequently showing that I'm up 2-3 pounds. It shows that and then all of a sudden (like last week), I'll be down those 2-3 plus maybe 1 more. But it seems my body is throwing a temper tantrum of sorts each week. I've done really well staying right around my allotted calories *with the exception of Saturday, which was my birthday- and I had chocolate cake!!*. I have had days where I've been 300-400 under my daily allowance and then days where I've gone 50 cals over. But it seems to even out nicely. My question is- how can I stop that mid week gain? I've been eating mainly fresh fruits and veggies, salads, grilled meat and veggies/potatoes sauteed with some olive oil for dinner.......no pretzels, chips, etc- no candy- none of the *100* calories packs of anything, etc. Honestly, it's mainly been fresh foods. I drink a good bit of water everyday and don't drink diet soda, etc. Any thoughts/help would be greatly appreciated. I don't want to quit this time, and I can feel myself getting discouraged, so I need to nip it now!