Nelie, it will get better. Your end of the tunnel was probably delayed due to the infection you had to fight off. I too, had a hard time dealing with the phlegm and ended up vomiting when I had to cough that stuff up. Suddenly it just started easing up and it was like the dark cloud lifted. The dark cloud will lift for you too and it's just around the corner.
Even now that I'm several months out now from radiation ending in March, I will occasionally cough up a small ball of crud. I'll either cough it up or my nose will start running and I'll blow it out. Gross as that sounds, it is a small reminder that those days really aren't so far behind me.
Keep your spirits up as much as you can. I felt like I was at my lowest point after treatment ended and I was dealing with weeks of being "on the ropes"
Jen