My singing voice keeps cracking and changing

My singing voice keeps changing every week. :( As soon as I sing a low song I cant get my voice to go high again it takes 1 hour or longer to get it back to normal. I cant even sing without my voice cracking. I cant even sing do,ray,me,so,la,do. [i think thats how it is spelt] I cant keep my singing voice changing to different notes. Say if I did do. Which is near the bottom of the scale , I would stay on that note for the rest of the scale. :(
If you get me. I like to sing and I have been trying to get a scolarship for north the highschool I might be goin to if I get in next year. The scolarship is for cultral like choir,drama or dance. It's been happening for 2 years now and it's really getting annoying. How can I fix my voice and what is wrong with it?

Did you resolve the issue of the lump in your throat you posted last week? If that's been going on for two years, you need to see the doctor. There's no way you can "fix" it on your own.

First, see a doctor to see if there's a medical cause that needs treatment.

Then, consult a good vocal coach.