I'm no medical expert, but as a fellow patient: It sounds like you're not "leading up to" an asthma flare: you're already having one! If you have an asthma action plan, you should follow your doctor's advice according to your action plan. If not, you should go to a doctor as soon as possible, inform them of how you're breathing, and ask for a written asthma action plan. If a doctor is unavailable to see you very soon, I'd suggest calling a medical hotline or something of the sort to see whether you need to be in the emergency room right now.

Your "feeling bad for weeks" was probably the leadup/beginning of your flare.

If an asthma education program is available in your area, I'd take advantage of it in the near future: it will teach you common triggers, how to recognize the early stages of a flare, and what to do when you're in a flare  (including when you should go to the ER). In short, it will give you all the tools you need to manage your asthma well so that if this happens again, you're prepared for it. It really helped me learn how to manage my asthma, and with the skills I learned from my asthma education program, I was able to reduce my emergency room visits from six in the year of '09 to none in the past year ('10). I was also able to go from needing three or four rescue inhaler refills a month to needing one every two to three months if I'm under control. It's a time committment, but it's totally worth it.

Get well soon, and I hope that helped!