I can totally relate!! I have weeks where I look back and feel like I couldn't possibly have eaten enough to keep me alive and then the next week I feel like I have eaten enough for four people.
After I started to take a look at what I was eating and what was going on in my life I realized that usually the week before my period I am eating a little more and for about 2 days into my period.
Also as time progresses you are going to be able to eat a little more. It is really important though that you pay attention to your body and stop when you are satisfied. If you start to notice that it is becoming a problem and that you are stalling or even gaining, then back to the basics! Measure and stick to the portion sizes.
Good luck to you

__________________
315/289/
169
Highest/Surgery/
Current
Goal to just be overweight 190
Goal to be "normal" 155
02/28/07 SURGERY!!
Month 1, -23.5
Month 2, -13
Month 3, -19
Month 4, -12.5
Month 5, -12 Century Club!!!
Month 6, -8 ONEderland

Month 7, -7.5 I am just Overweight now!!!
Month 8, -8.5
Month 9, -6 Single Digit Pants

Month 10, -1.5
Month 11, -2
Week 47, -1