Concerned about low Peak Expiratory Flow Rate

I was diagnosed with asthma at 16 after getting pneumonia. I never used an inhaler and still presumed swimming 4 days a week. I'm now 30 and just recently quit smoking marijunana after 10 years, never touched a cig in my life.

To top it off I suffer from GAD (generalize anxiety disorder and OCD). I read an article yesterday about marijuana and emphysema at a young age. This put me in panic mode and I quickly made an appointment with doc to been next week. I even went out and purchased a brand new FLOW PEAK METER made by omcrom. I came home and tested, my numbers were really low at 450, the highest was around 500. The normal rate for someone my age and height is 622. I'm barely at 450. I'm only 150lbs, not sure if this has any affect to score.

The meter I purchased 1/5 star reviews on amazon, mainly about the quality but some are complaining that the meter always shows 80-100 lower compared to other meters Not sure what to make of it. I'm scared and can barely focus. I just had a son, now I'm afraid I wont be around to see him grow up. I have no wheezing or any asthma attacks in my whole life.

Is there anything I can do to get my rate to normal or is it downhill from here? Please any insignt or reassurance will be helpful. I'm new to this.