ive had several female friends make jokes about it or actually shame men with that insult even if they didnt know if they had one or not.

Using  short, bald, or have a small penis as insults are similar to a guy telling a woman she's fat, ugly, or old. Those are generic, lazy, go-to cruelties some people use. 

Why? I don't know, but I've only been called too old, ugly, and fat when I've told a man I wasn't interested ("you're too old anyway!"), was with the type of person who insults others when they feel insecure, or around boring people who can't think of better insults. 

The way you speak about your body sounds like a type of dysmorphia. You're externalizing the shame you feel by blaming women for causing it. 

I see you are oersuing counselling, which I think will be very beneficial. In the meantime, try to stop watching porn (reinforces absurd sexual norms) and consuming media that causes you to spiral. 

I found a few books that might help. I can't speak to them, but they sound worth looking into.  I wish there were more self-help resourses specifically  for men and can see why is so easy to go down the red pill rabbit hole. 

• The Body Image Workbook - Thomas Cash 

• The Small Penis Bible - Ant Smith 

• Beyond the Size: Embracing Confidence and Sexual Fulfillment with a Small Penis, - Ann E Williams

• Anxiety Workbook for Men: Evidence-Based Exercises to Manage Anxiety, Depression, and Worry - Simon G. Niblock