vocal nodules? HELP!!

Two years ago, I started singing, but I was using bad technique and I was straining my voice to hit the high notes. This continued one to two hours every day for about 5 months, then i stopped, because the lower range of my voice would start sounding rough after singing for a few minutes. After about one or two months, I started singing again with improved technique, and my voice stopped becoming rough.

However, after a while i began to notice that the highest notes of my upper range were disappearing. They started to sound airy and they would cut off while i was singing those notes. The rest of my range stayed normal. The problem is, I dont know if I was able to sing those high notes clearly when I first started singing. Has my voice been damaged or is my vocal range just expanding?

Recently, I have felt like I have excessive phlegm in my throat, but this could be due to allergies. I also feel like my voice quality is not as good as before. Am i just being paranoid or do i really have vocal nodules?

I am a 14 year old girl if that helps.