You shouldn't take Claritin-D longer than 7 days. If longer, you may be simply suffering from allergies and should have allergy testing and possible drops or injections. (the drops have helped me!!)
Otherwise, you will start having reactions of too much of a good thing (pseudoephedrine) meaning, dizzy, blood pressure issues, etc. Believe me, I experienced this and learned. Check with your doctor if you're not better after a week on the OTC meds.