I am experiencing severe nasal congestion. i'm very prone to sinus infections. can i take phenylephrine and pseudoephedrine together to max results?

No: There was a recent study showing that phenylephrine was not effective for congestion. I would just take the pseudoephedrine. You could combine that with an intranasal steroid or nasal rinses.

Better not: Use only one, preferably the pseudo ephedrine, but be cautious when using either if you high blood pressure. If you're prone to sinus infections , better see an Allergist/ Immunologist, check aaaai.org or acaai.org for an allergist in your area, meanwhile, saline nasal washes, OTC steroid nasal sprays would help you better with the congestion, good luck