Yellow mucous down back of throat 4 weeks after sinus surgery (including sphenoid) and septoplasty. Is this normal?

It has been 4 weeks since I had sinus surgery and a septoplasty. I have been doing nasal rinses with neilmed 4 times a day and am still on flixonase nasule drops. In the past few days I have been getting bad headaches behind eyes and pain when bending over along with yellow discharge down back of my throat. I don’t think it’s infected as have no other symptoms such as bad smell or fever. Is this normal? Is it likely to be infection? Should I still be getting sinus headaches now? Thanks