There is a difference between being aware of
and getting lost in, an experience:
the later often leads to thought filled roads.
It's nice to hear that you have deepened your yoga by inviting awareness into your practice. I agree with you, yoga is more than just stretching, strengthening, and keeping fit ? though, it is those things as well.
As to your difficulty in keeping attention on the breath while you practice, that is something I have struggled with as well. One thing I have learned is that focusing on the breath is not the only way to deepen our yoga, or for that matter, for meditation in general. In fact, I spent years struggling with focusing on the breath as a meditative technique until I found what worked for me.
The truth is, breath meditation is not for everyone. For me, touching in with the sensations of the body is the most effective way I have found for myself to invite a meditative state. Through this technique i have, over the years, come to experience Samadhi on a regular basis ? and that is while moving from one asana to another.
We do not have to be still, sitting on our butts, doing special breathing techniques in order to meditate. The key in my experience is to find something you naturally rest your attention on. If you are a visual person, than visualize the energetic qualities of the asana. In other words, if you are doing the cobra, be the cobra.
If on the other hand you find yourself attending to sound, then be with the sound. If that is a fan, the sound of your breath, mantra, or whatever else, experience the vibrations.
If you are into touch, as I am, then feel the energy. Let go of the posture, the thoughts, and everything else and sink the attention onto the feeling sensation. Subtly tweak the postures to feel the differences in energy.
That's my experience.