I am sorry to hear that you are dealing with chronic sinus congestion. I strongly suggest that you go back to see either your primary care doctor
or an ENT (ear, nose, throat) specialist about this issue to help you figure out what your next steps should be.
If you read on the internet about chronic sinusitis you will find a lot of information about various diets for relieving sinusitis. However, none of these dietary changes have much evidence behind them that they actually work. This is because the allergic triggers for sinusitis tend not to be foods but, rather, allergens that you inhale in the air - things like mold, mites, and pet
Your doctor will be able to help you figure out what allergens might be provoking your sinus congestion. This might require allergy testing to help figure out.
They will also be able to help you settle on a better treatment plan that doesn't just involve taking steroids frequently. For example, you may need to use a daily anti histamine or other anti allergy pill, and you may need to at the same time use daily steroid nasal sprays. Also, ask your doctor about nasal irrigation with saline solution, which is helpful for some cases of chronic sinus congestion.