Can i take clariten d and mucinex (guaifenesin) cold and congestion together for the best results?

Yes: I don't think the Claritin will help much but the "d" will shrink the nasal linings and improve airway. Make sure the Mucinex (guaifenesin) doesn't contain decongestant if you are taking Claritin d. Mucinex (guaifenesin) helps to thin secretions but works better when hydrated. Consider nasal saline rinses a few times daily, humidifier, and 3-4 days of afrin.