You may have a deviated septum. I do and I sympathize with you.
The obstruction could be nasal polyps, which would explain the sinus infections.
They can make you more susceptible to sinus infections that recur often or become chronic.
If this is the case indeed, you may need to have endoscopic sinus surgery.
An experienced ENT surgeon will be able to diagnose
and do the surgery if necessary .
The nasal lining-the nasal mucosa- could be damaged by the inflammation and other factors- becoming itself a cause for complications, one of them being crusting from the bleeding of the compromised mucosa.
And in the event polyps are ruled out, the latter would be the other possibility.
I would also rule out fungal sinusitis (there are 4 types) and also any other fungal overgrowth, in light of all the antibiotics you took.
Best wishes,
Niko