Accidental plagiarism?? Maybe?

I do all of my work at the library and tweak grammar/spelling when I get home. Whilst writing the essay I was struggling to form my own example of the mesosystem and so looked online for some examples to give me an idea of my own. I found and watched a YouTube video which explained the system really well so I included that in my essay, highlighted it as red to make sure I changed it and formed my own when I went home that evening. I did go home and create another example in a different word document with the intention of including it in my essay before submitting. The day of the deadline I had skimmed through my essay, highlight the text to make it new times Roman and clicked black ink. This erased the previously highlighted red ink and I was completely unaware that I hadn’t included my own example. It wasn’t until I decided to look at the date which we’d receive our grade back that I skimmed through the essay and saw it highlighted as a high similarity percentage that I began panicking and realising my mistake. Initially I planned to resubmit the essay but realised I’d then be gapped as a late submission so decided to email my tutor and I am still waiting for the response. I put a lot of effort and research into my essay and would never intentionally hinder my grade by plagiarising. I am extremely upset, stressed and sorry about this. At the time of this my Grandmother was at hospital due to having an operation as she had lung cancer and I was not in the best frame of mind in terms of attention span. I understand this shouldn’t be used as an excuse for my negligence but it was a genuine mistake. I submitted the essay on the 29th and it’s the 20th now, nobody has emailed me about it or excuses me of plagiarising and my plagiarism score was 15% but 7% of that was for the four lines marked as from a website that I hadn’t even used. Really worried as I get good grades of about 70% so I’m panicking that I’ve just ruined uni for myself.