I need help smoothing my tessutura into my falsetto?

I am a tenor, and I use to be a very high counter tenor, but then i turned fifteen, and I was happy, but now I wish that I had a little more of a range, it's sort of limited at the moment, I have a great lower and medium register, but I'm having a lot of trouble with higher notes, that most tenors can reach, and so I guess i'm more of a baritone tenor. i've been doing drills after drills and it is not working, everytime i try to sing something ped the high D I croak like a frog, and it sounds terrible, i am a great singer, and hope to one day be a primo uomo. I am fifteen years old, and would also like to know how i can make it in opera or broadway, i'd be happy either way, i am going to start acting lessons plus the numerous roles i'm going to do at school, and i take ballroom dance lessons, and will be starting ballet in a week or two. I am currently studying german and italian, and took french and spanish.