Lauren,
I don't have much more to add, as I think everyone is doing a pretty good job. I also know the feeling of thinking its too soon for antibiotics. I avoid them at all costs if/when I think there is a fleeting chance my body can fight off some of what I'm experiencing. Because of this, I am sensitive to many antibiotics yet. Plus, when I do go in for clean outs, its usually when I can tell my cough and stuff is different.... This last time my pft's weren't even down and I went in cause I just didn't feel right. However, there are several times within a given year that I feel crummy and congested and run down, but I don't always run to get on IVs unless it just never lets up. So, I guess what I'm saying is listen to your body and not so much how long its been. Maybe the meds you were on didn't catch the buggies that are bothering you now.... Maybe they need to try a new combo. Often, what you show on a culture may be from a certain part of your lung and what is actually causing you problems may not have "come out" to show on that culture. So, maybe the drug combo was inaccruate because of that. I don't know. Just some thoughts on why you may not feel better. Hope that helps put your mind at ease that it may not be that you're "sicker", just a different bug is showing up that you need to "attack" with antibiotics.
Either way, if it were me, I'd watch it a few days and if my body can't fight it, I'd go back in. With changes of seasons, pollution, etc... I know my lungs act up sometimes and I know my pfts would be worse at these times, yet I wait and see what's going to happen. It isn't always my PA acting up (and I colonize PA constantly.. various strains of it). Just me though. Get into the doc if you don't get better. <img src="i/expressions/face-icon-small-smile.gif" border="0">
Good luck!