When we step foot on the astral we walk between the worlds (physical and spiritual). A piece of our conscious mind drifts away, allowing us to explore. Some people live everyday in such a way that allows them to be aware of both sides naturally, but it is not the same concept as astral travel. What it sounds like to me is that you didn't bring yourself all the way back when you traveled. You aren't fully grounded back in your body and are viewing and hearing the astral because you're still floating around while in control of your body. While this may seem like a nice thing for some, it isn't good for you not to be 100% "awake". You're consciousness is somewhere inbetween and you need to restore it for your own health on all levels.
I would recommend not attempting astral projection for a few days and focus on your physical being. You need to ground yourself well, and as was suggested above, cast a protection on yourself, and I would also recommend protecting your home or at least your bedroom too.
Meditate as if you are going to project, but reverse it, and really FEEL your body, experiences your senses fully, and bring yourself into full awareness of the physical. Pull all that is you back into yourself. Feel your consciousness come back. If during your meditation you feel a floating sensation, you need to pull yourself back into your body slowly and reinforce it being there. Eat and drink something afterward and truly taste and enjoy the food. Pick up an object and study it with sight and touch, or take a shower and feel the water as it strikes your skin, smell the soap, etc.
When traveling, it is very important that when we are finished traveling, that we return exactly as we left and ground. Coming out of it quickly or just opening our eyes and moving around doesn't always bring our energy back to where it was. And that's what I believe happened with you.