Mental Health Support

I would think that you'll have to level with your SO and tell her exactly what the problem is. It would seem rather insensitive if she knew that you had this problem with your thumbs and didn't understand or care about what you were going through trying to get those bags open.

In other words, I don't think this is all your fault. Aside from the gouging of your cheeks, it seems to me that being angry in that situation would be a perfectly normal response. Just try not to hurt yourself like that. I hear that makes some people feel better, but it's not a good deal.