Your answer to “How can I know I’m doing what the Lord wants?” is to “Get confirmation from someone who doesn’t know what I’m thinking of doing”, could you please be a bit more specific.
Some times confirmation comes when a believer exercising the Spiritual Gift called Word of Knowledge (1 Cor. 12:8) tells you something they have no way of knowing. Often they’ll say the Lord sent them. For example, say I ask God if something I want to do is in His will for me. If someone comes up to me and starts talking about it in specific terms , even though they had no way of knowing I was interested, it’s likely a confirmation from God.
Other times confirmation comes in the form of help you need but haven’t asked for, like doors being opened, or the money you need being provided. Confirmation can come before you begin or just after, but because the Lord wants you in His will, if you ask in faith, He will answer.