I have been concerned lately. I saw a doctor recently because I felt a lot of sinus pressure and have been very fatigued. They prescribed me an antibiotic and some Claritin D24. I've been taking them for a week but but my symptoms haven't gone away. I am also now having back pain and a stiff neck. I'm concerned because I am fatigued to the point where I can't do much and the pressure is of course very uncomfortable. Does anybody have any ideas or suggestions. Am I possibly resistant to the Antibiotics? Can Sinus problems be connected to neck stiffness and back pain? Am I having symptoms of anything else.