If you didn’t recognize it, then you may have something to worry about. The fact that you feel guilty is reassuring in that you are not so far down that you’ve lost sight. Have you considered medication? I may have missed if you answered that. I know you said you managed before without, but oftentimes the additional strain of motherhood takes just riding it out off the list of options. It may be time to accept pharmaceutical help.
And you didn’t do this; you can’t undo this--so there is absolutely no need (or room) for guilt. Guilt leads to self-pity which is the opposite direction than the one you want to be heading. Kick that guilt’s ass, humble yourself, and ask for help, sweetie.
And I echo a previous comment- look into supplements, especially if you are anti-med ( which I totally understand, as well), but either way. Making sure your body is balanced is crucial.
You deserve to enjoy this time with your tough, not so tiny anymore, bundle of joy.