Frequency modulation of $m(t)$ in MATLAB
Integration was incorrect. I was integrating it with $dx= 1$. Doing m(j)*1/Fsoperation in the for loop, I have made $dx= 1/Fs$ now.

As can be seen, frequency changes for different amplitudes now.


Moreover, resultis a constant, it should be changed toresult2 so that it gives result with respect to time $t$.