Yes, shedding can last quite some time. Then of course you go through hair cycles too. The hair cycles in and out. I would stay on it if I were you. You are probably just going through another shed. With every shed, your hair should improve each time when it grows back. Good luck!
Ditto what Kalika said, sheds can last a long time but usually signal a good response to the treatments. Stick with it, the shed must be about to end and regrowth should start soon.