Low PF

Hi, I'm new to the forum and have a question.

My asthma is relatively mild, and I only really tend to struggle during exercise and when I have an infection/cold. I was diagnosed 2 years ago and was on Ventolin with a clenil preventor inhaler until October 2013, when I had my first bad attack and ended up in hospital. Since then I've been on ventolin and symbicort 200/6 (1 puff twice daily).

I've had a string of colds over the winter and finally went to the doctor on Monday, who said I have an infection called tracheitis. My lungs sounded clear, though I was a bit breathless and PF varying between 300-390 (PF normally 450). I was put on antibiotics for 7 days along with double my usual symbicort dose (which I've been doing since last Saturday), and told to go back if PF dropped below 350 and stayed there.

Since then, my PF has been wobbling between 340-370. Last night it was 400 (highest since last week) but this morning it was 320 when I got up and now sitting at 350. The question is: should I go back to the doctor? I know they said to go back of PF continued dropping below 350 but the thing is that I don't feel particularly wheezy/breathless. Just exhausted, a bit lightheaded and coughing up thick sticky clear mucus. Is this my asthma, or do I just need to be more patient with the antibiotics?

Thanks, and hope everyone is as well as can be.