My question is should I go back to allegra (fexofenadine)-d or take the regular allegra (fexofenadine)?

Allegra (fexofenadine) alone. Allegra d contains a decongestant that is a poor long term option. If you are dealing with chronic nasal congestion i would recommend alternative treatment such as a nasal spray like nasonex, (mometasone) flonase, etc.. These are more effective long term options for nasal congestion due to allergies or other triggers.