Im already tuning a guy but this other guy wants me aswell ??? what to do/?

ok so i am already been tuning this other guy and we arent like dating or anything but yeah :) so now this other guy is into me and he knows about guy no.1 and is texing me all the time and then when i dont reply hes like so what if i was jake* ???? and i dont want to just tell him im not interested cause hess so sweet and hes friend told me i would break his heart how do i tell him im not interested when clearly im into this other guy and he knows that...