why do I sound terrible when I record my singing with a mic?

IM GOING TO CRY.
I’ve never sang for anyone before but always told them I sing great. My mom is putting me in private voice lessons and choir. The choir expects me to be a super good singer because they all aren’t good singers.

I just recorded myself singing a couple easy songs like The Prayer and I STINK. I ABSOLUTELY STINK. I can reach high notes but they don’t sound good. it sounds like I can’t hold a note. If I sing for people, they’ll think I’m a liar!!! I read around that its my real voice. THAT ABSOLUTELY CAN NOT BE MY REAL VOICE.

My brothers, all three, the only people I’ve ever sang for, say I have an amazing voice – like I sing like Jackie Evancho, and they rated me NINE OUT OF TEN.

I used a 2005 iMac mic. Is it the mic!? please help me… i’m absolutely devastated.