Mango string getting stuck between one's teeth

Q: If a mango string is stuck in my teeth, I did my best to clean my teeth before making ghusl mindful that all mango strings are taken out, after ghusl I read salaah and quraan. The next morning I ate thereafter I cleaned my teeth again and I found a small single mango string from my teeth. Is the ghusl, salaah and reading of quraan valid? The mango string is as thin as hair.

Opinions and remarks of people

Q: I am a Muslim guy in college. I have a problem that is making me very depressed. Whenever I decide to do something I always think; a.) "what would others think about this?" plus I b.) fear that they would discriminate and think something negative in their mind about it c.) hoped that they would like and approve it. This is really affecting my daily life and studies, this is so strong that even when I'm praying salah alone these is always what's in my mind. So my questions are:

1.) is this counted as Riyya? Since my niyyah for studying in college is for the sake of Allah (which ulamas say is now a form of worship). When I go to school, do reporting, studying, taking quizes and exams etc. these thoughts pops into my mind that I lose concentration, focus and become very anxious to what their thought or reaction is.

2.) How can I remove this? Before in highschool I always think about "what would Allah think?" but now these thoughts are the top concerns in my mind instead of Allah These are making me very depressed. I can't study well and it's really affecting my grades plus my parents are paying for my education and are getting old. I want to finish so that I can provide and take care of them but these thoughts are hindering my progress.