Insanely weak back

I am currently almost 14 and have an incredibly weak back. I have tried doing pullups or dumbell rows and other excercises for upper back, but i cant seem to do anything about it. I feel like i just need a little more strength to do the workouts, but i just cant seem to find ways to increase my strength. Ive tried doing assisted pullups, but i cant seem to feel it in my lats at all.

Do you guys know what i can do about this