I've had sinus infection symptoms and have taken mucinex, (guaifenesin) i had very bright green diarrhea and a little blood in it as well, should i be nervous ?

Little relationship: Mucinex (guaifenesin) or guaifenisin is a mucolytic agent which tends to liquify tenacious mucus secretions in the lower respiratory tract. I am not sure it has any harmful effect on the GI tract and the green diarrhea is not related to sinusitis. You may have a viral infection that effects both the sinus area and the GI tract but they are separate problems. Consult your physician.