I had childhood asthma no probs for 10 years had an asthma attack 2 weeks ago still worsening peak flow is <100 what to do steroid antihistamine used?

Hospital: You should be in a hospital right now, or an emergency room. Several options are available to you.

Steroids/albuterol: I would suggest that you use inhaled albuterol and some form of steroid preparation for your symptoms. Based on your recent history of an asthma attack and low peak flow, you should seek medical care to determine whether you need to be admitted to the hospital. If they can manage you as an outpatient, determining the dose of the steroid and whether it is in an inhaled or oral form is suggested.

PFR : If your PFR is under 100 , you need to get to the ER to get treated immediately. Unless you are 2 feet tall, your airway is severely obstructed. Don't wait another second.