Yeah, I'm also firmly in the too far forward club. For me it's muscle memory. Even when I think I'm so far back that I'm going to fall over backwards, my shoulders are still too forward. It could also simply be your saddle is pitching you forward. Either way, here's a few things you can try without the help of lessons.
1. At the halt, stand straight up in the stirrups. Find your center of balance as if there were no horse there. You should be able to stand straight up without holding onto your horse for balance. If you find this exercise completely impossible no matter how many adjustments you make, it's the saddle, not you.
2. Assuming you were able to do exercise 1, now build on it. Stand straight up, then sit almost back down, but stay hovering over the saddle. That's the correct two point position. You will probably find your shoulders farther back and your thighs on fire when you arrive at the correct position.
3. Once you can feel the position from #2, try it from a different direction. Sit in the saddle and then simply shift the weight into your heels as if someone was tugging on your heels to arrive again at the 2 point position. Nothing should happen with your upper body, The lowering of the heels automatically brings your butt out of the saddle, closes your hip angle a bit which inclines your upper body foward.
4. At the walk and trot, practice going from full seat the half seat. At the trot, get a nice rhythm going and do 4 beats posting, 4 beats up in half seat. If you can, add 4 beats of sitting as well.
5. If it's just a matter of weak legs, hike your stirrups up as short as they go and ride around like that for a week. It'll hurt like crazy, but you'll have rock hard legs in a short amount of time.
Hope this helps.
You just have to see your distance...you don't have to like it.