Speaking form personal experience, the breathing meditation you did is what spawned the ability to be mindful of your physical state. This is because in order to successfully breathe into various areas of your body, you have to be mindful of that area. It is directly practicing physical awareness.

The fact that you have become aware of subtleties of flight-or-flight responses is extremely good. That's stage 2 of what it is possible to be mindful of.

Stage 3 is emotions. Try purposefully creating emotions. Try listening to music, and enhancing the emotions you feel from the music one at a time, and slowly. Try changing your emotions the same way you breathe into different parts of your body. Try creating an emotion when you breathe in, and letting it dissipate when you breathe out.

Stage 4 is thoughts. Stage 5 is intuition. Stage 6 is deep subconscious data grouping and relationships. Stage 7 and 8 are a lot more complicated. Stage 8 is what Taoists call "the Tao".

At stage 4, you should also begin practicing what is called "dissolving" in Taoist meditation. That's the ability to be aware of a stuck thought/feeling/whatever, and allow it to dissipate. Methods of doing this involve breathing into the very precise spot you feel is tense when you become aware of the stuck feeling, or slowly stretching and contracting that spot to get the tissues and fluids moving; and may also include image training to imagine that spot liquefying, then gassifying, then becoming a part of your breath so that you can breathe it out. The trick is to become as aware of the stuck feeling as you possibly can, and then relax it slowly. It's necessary to realize that your thoughts and feelings are connected to your fibrous body tissues in order to accomplish this (for example: thought control is connected to nerve tissue control).

Be careful of image meditation. If you choose to go beyond halfway through the path of meditation, you will have to remove all of the images you accidentally lock into your body.

PS. "stages" overlap. "stage" is a loose term I came up with to describe it just now. The Taoists call it "the 8 bodies". They're just a reference so that you can know what is possible, and approximately how much effort is required in order to accomplish it. Half way through, the game changes. All of the way through, the game changes again.