I would go to a singing teacher and explain what sort of music you sing , where you sing etc. Only someone who is in the room with you can spot and correct things like posture and the way you are breathing.They will give you aids to memory to help with this, but it needs to be part of a conversation rather than typed words which can be misinterpreted.For example, I tell the children at school to remember not to "get thinner" when they breathe in .In the warm up I also get them to watch each other for raised shoulders on breathing in and to correct this - and poor posture- in each other. We talk about, "Singing further" rather than louder. This would be meaningless and twee to you unless you had been in the school conversations.

Whatever you decide to do, enjoy your singing and discovering your own, unique voice!