Why does my brain do that?

Yesterday, Theo had his 9 month check up.  We got to meet our new doctor, and I had all my questions answered.  The doctor was impressed by all of Theo's sweet tricks, like cruising and having an odd number of teeth.  But one thing about the appointment upset me a bit.

Theo has always been in the high 90th % for height and weight.  But at 6 months, two things happened: he started crawling, and he started eating solids.  I knew babies thinned out when these things happen, but when the doctor told me that Theo was in the 9th % for weight, I was surprised. 

He's still like 92% in height, but really? 9th in weight? Imediately my mind jumped to, "you're not feeding your child!  How could you not have noticed! Terrible mother!"

But of course, the doctor explained to me that since he's progressing well and doesn't act hungry or grumpy through the day, that he's probably fine.  Babies find their own balance for eating, but bring him back in a month and we'll re-weigh him.

What part of the brain calls you a terrible parent whenever you or your child isn't perfect?  I have a whole list of logical reasons why I know I'm not a terrible mom:
-I love my son
-he's a happy, healthy baby
-I'm a first time parent, so I'm still learning
-etc, etc, etc

But still, it's pretty annoying to have that silly, illogical whisper in the back of my brain, "Don't you know better? Well, you should."

Of course I'm a good mom.  Would he look this cute otherwise? Come on.

But I'm just taking this as a learning experience, and giving Theo lots of extra opportunities to eat.  I think by the end of today, he was sick of looking at food.  Maybe that's why he went to bed at 7 instead of 8:30...