Good fertile question. You must get a lot out of this music, or you wouldn't have put all that time in to make the progress you have. (Some posters seem to have forgotten to give you credit for this.)

No doubt about it, singing is made to be shared, and loneliness is rarely inspiring.

If you sit down to sing spontaneously outdoors, and don't like how the open space attenuates your sound, try positioning yourself near vegetation or surfaces which can reflect it back.

Please let us know which suggestions work for you.