How to know if I sing well...?

Just by listening to myself,without even recording or anything.Or if that can't happen then with recording.How do I know that I am a good singer.Personally,I like my voice but only two people in my life told me that I have a good voice when singing,so I don't feel that I am.I am a bit shy to sing sometimes and that makes my voice seem bad,but when I am alone I sing loud and to my opinion well,but I need to make sure that that is the real "well".Thank you all!Love you!Mwah!♥