I have chronic sinusitis and also use Afrin. However, my doctor has me on watered-down Afrin. (Use saline solution to fill the partly empty Afrin bottle when new), followed by Flonase and Zyrtech.
I also use the Grossan HydroPulse nasal irrigator which I couldn't live without. The irrigator both stimulates the cilia hairs inside your sinuses, promoting drainage at the back of your throat. It also cleans out phlegm, but uts primary purpose is to promote sinus health.
Use the HydroPulse with saline first to stimulate your sinuses and eliminate some of the phlegm. Then two sprays in each nostril of the watered-down Afrin, which reduces swelling so the Flonase, a steroid spray, can reach into your sinuses. I do this regimen twice daily.
Before starting this, you should see either an allergist or ENT doctor to make sure this regimen is appropriate for you.
Yes, it can be irritating to you nasal lining after longterm use. You have to wean yourself off of it and it is very hard because you get the rebound congestion. My sister had probs with it and started using it in only one nostril for a few weeks, then decreased down to one spray, etc. Best of luck to you.