I've been taking this medication now for a few weeks; helped my acne a ton and seemed to be going good. Just this week though, I've started getting really nauseous after taking it and violently vomiting after which I feel okay. I'm wondering if I'm becoming sensitive to it all of a sudden or it took a while to get into my bloodstream? Also, I have been having the worst upper back pain and it was hard to breathe; I thought maybe I pulled a muscle but the side effects list "pain"- does this have anything to do with it?