So grossed out right now

Discovered lice on Shawners yesterday. Been bagging and washing bedding, stuffed animals, clothes, and pillows since. Am SO exhausted. This is the THIRD time one or both of the boys have had lice. What the hell?! Myself and every other person it seems only experienced it once in their childhood. I feel like a failure. The first time was from school, understandably, the second Justinbustin got it from a youth group sleepover where five other boys had it, also understandably. I think what gets me this time is I have NO IDEA where it came from. I've been racking my brain. M's little girl had it a few weeks ago which is the only place I can figure it came from via me who's been over there several times. He's been watching their dog the past two days (another vent that I'll just have to copy and paste from texts to KT - EVERY time I watch their darn dog something stupid and crazy happens), too, so my mind instantly jumps to that. BUT he's been scratching for a few weeks. I've been checking his head and have seen nothing. Even yesterday I checked his head and saw nothing. I decided to take a comb to his hair because I had thought he was allergic to his shampoo but he was still itching after we switched it. Out came a ton of nits and lice. SO DISGUSTING. I had a crying meltdown on the phone with my mil today because I feel like a total failure. We've gotten rid of it so easily before that Shawners doesn't even realize the impact of it. I've had to explain to him it's best if we buzz his hair so we don't miss any nits, that he needs to assist in bagging everything up, and when friends spend the night they HAVE to use a separate blanket and pillow so they can be washed afterwards. They've been especially bad about friends using whatever blankets or pillows they want and then throwing them back into the mix. That's the only other place I can think of that it might've come from - a friend spending the night who didn't know they had it. I'm so grossed out and feel like a failure right now. And so exhausted from all the washing and bagging.