Have i outgrown asmtha?

Ok ever since i was like 8 i would go to the doctor and every 3 months and get a regular check for all bodily things. And my dad told the doctor that I weese sometimes in the sleep, she suggested asmtha. Let me tell you several times this doctor thought i had a disease and we got it tested and i neva had 1. So we got this tested and they say technichly i have Asmtha due to small lung tubes. So after 2 years i moved and i went to a new city. my doctor gave me a peak flow thingy and i always use it. after 2 more eyars we saw the number go up, more, and more. now when i take it my personal best out of 3 is 300. is 300 a normal number for a 12 yr old, very good health, and 180 lbs(alot is muscle)?