You should not judge yourself.
You are not a veterinarian.
You are not a pyschic.
You did what you thought was right.
You tried.
You cared.
You loved.
Otis knows you loved him.
Otis would not want you to feel guilty.
Otis loves you.
Wow, I'd never heard of that before but I found this: linky
It certainly sounds smart that your specialist is doing a tick panel.
I hope she feels better soon.
The glands are - of you picture the face of a clock - at 8 & 4 o'clock or 7 & 5 o'clock with the anus in the center like the clock hands rotate.
Boy, I hope someone can find a diagram cuz I don't think I'm explaining it well.
Some folks will comment theat their grey did a lot of butt licking prior to a rupture. That wasn't the case with Gracie, though she would lick occasionally. Nor did she do any butt dragging on the floor.
The vet said it was a good thing it ruptured as that relieved the pressure. Antibiotics fixed it and there was some powder as well. The details will be in that post link.