Hey there...first, Congratulations on 2wks quit!!!! You have made a hard, but good decision in quitting both. You are young, too...which is in your favor.
My story was the same when I arrived at MH in 2007. Quit both cigs and pot, July 2007. At first I felt Great; had enough energy for 3 people. I learned (from this forum) that that was from the oxygen I was now getting. Soon I suffered SEVERE anxiety, insomnia, night sweats, strange dreams, all you describe. The diarrhea is normal, as well...as is the itching. I never had any itching, but I've read on here, some people have. Yes, this is ALL withdrawal. I went through this several times (due to relapsing), and each time took up to 4mos....but at least I knew what was happening and that it was normal. Everyone is different, so it doesn't necessarily mean You will go through w/d for 4mos...but it *can* go on for some time due your body ridding itself of all the carcinogens and chemicals in cigs...and pot nowadays. There is like 4000 chemicals in cigs alone. Just awful.
I'm not sure what to say about your shower incident. I think it might be just coincidence. .
You are going to have good days and bad days...just like anyone quitting a substance. Do some research, honey. The website - whyquit - is a great place to start.
You may want to visit your Dr in order to ease your mind. In fact, I would recommend it. But what you describe is most likely withdrawal from the 'event'...and it IS an 'event'.
I wish you the best. Stay clean! Big hug!!
Please keep us updated; we care.
I see several people answered your question in the Hep C Community. I hope they were able to ease your mind.