First, are you taking lessons? If not, find a good vocal coach.
As the comment pointed out you are may be at the age where your voice is changing. But in general all people have notes where they change register and those are notes that require lots of training to learn to control. My first break point is at Bb3, right before middle C. It is what it is. I can sing a whole octave or more above that without a problem but right at that note things get messy.
The ability to control the timbre of your voice depends on support (your ability to control the flow of air from the diaphragm), and the shape of your mouth. So it is possible to get clean intense sound in the upper register but it takes work and training.
It is not possible via a blog site like this to assess what is going on with your voice and provide a one line fix for it.