I have/had a similar poo/pee problem, got "sniffed out" by my 2nd grade teacher when I went in my pants, even though we had our own bathroom in the classroom, so I have a faint idea where you are coming from. I'm 62 now and still usually go to the bathroom mostly in the middle of the night when there's no one to see/know/yell at me, etc.

I eat a lot of popcorn (poopcorn :-) for the fiber (I usually try for for 25-35 gms a day) and because I like it; it's a whole grain so good for one on several levels. You might try something like that?

For the leftover difficult/ugly childhood, I recommend therapy. And I'd think twice about bothering with studying something that you don't like; that just makes things harder for you, not easier. I was majoring in my #1 subject but my last year changed to another subject and did not get back to it until my 50's; a lot of "I wonder what it would have been like?" thinking after that. It all did/does come out all right in the end (sorry for the multi-layer pun :-) though.