Persistent Vocal Issues - Please Help!

[hermione1]

Last month, I caught a bit of a cold. Stuffy nose, extremely sore throat, the usual. This month was a full month of performances and rehearsals, and I was lucky enough to have recovered before everything started up. Or so I thought.

However, as soon as I started singing again, I noticed that I was having issues. It was harder to hit high notes (not very high, just past a soprano C), my voice felt unstable, I would be phlegmy afterwards and slightly hoarse if I tried to sing again, and I had a feeling of breathiness in my voice.

After a few days, it would subside. However, the next time I had a rehearsal, the exact same symptoms would appear. This has been happening for the entire month, and I'm growing concerned. I don't believe I have vocal nodules or polyps, but this doesn't seem like a stress thing either.

Can anyone tell me what is wrong or recommend a course of action to take?