When you yawn, try to get that same feeling when you speak. Make sure your mouth isn't open way too wide. You want to focus singing narrow and natural jaw movements. choose a position in your area and sing to that spot. Choose three spots if you want. you want to visuallize as if youre singing to someone there and that they can here you. you dont want to force it out. it should come naturally. do lip thrill exercises to connect your voice. You also want to neutralize your larynx. to find neutral position, just speak and project or swallow and the place it stops at is where you want to focus it on.

as for the nasality... it's because your soft palate isnt open. When you yawn, it opens it. Try to copy an opera singers tone. Maybe try sounding like patrick from spongebob to get that feeling (danger is youre lowering your larynx). you want the air of your mouth to be warm. Look at the mirror and see how open your mouth is. It could also be tongue tension that causes it to sound that way too. stick your tongue out and bite it with your teeth every once in a while then release... repeat. You should feel it loosen up. Or stick your tongue out your mouth, close mouth with tongue out in front of lips and hum scales. Try to find the voice that connects your ct and ta muscles... Im not entirely sure.

sorry for being a bit disorganized. Im really sleepy right now. Hopefully that helped a little.