The fear of man is a snare, and you have felt its teeth. The good thing is that you are already seeing the real issue. It is not that you are quiet. It is that the fear of others can become a trap that keeps you silent when God would have you speak. You noticed the midwives in Exodus, and that is exactly the right contrast. They were not bold because they had outgoing personalities. They were ordinary women who feared God more than they feared Pharaoh. That reverent fear of God is not the same as being frightened of him. It is awe. It is taking him so seriously that his approval outweighs the opinions of everyone else.
That kind of fear is the beginning of wisdom. It rearranges your heart. When you fear the Lord, you learn to hate evil and to depart from it. When you fear people, you step into a snare. Scripture says even strong people get caught by that snare and do foolish things under its pressure. So the goal is not to become an extrovert or to manufacture a public speaking personality. The goal is to trust the Lord enough to obey him in the small moment he gives you.
Your ease behind a screen shows that you can communicate. What makes you freeze in person is not a lack of ability. It is the immediate presence of people whose response you cannot control. That is a form of the fear of man. The answer is not simply to do it scared by gritting your teeth, although there are times when you will act while still afraid. The deeper answer is to ask God for the love that casts out fear. Perfect love, the settled assurance that you are safe in Christ, drives out the torment of needing people to approve of you. The more you know that God loves you and that you are hidden in his Son, the less power the fear of strangers has over you.
This also means you are not meant to rely on your own strength. Your own strength would try to turn you into somebody else. The Spirit works differently. The preparation of your heart and the answer of your tongue come from the Lord. He is already at work in you even when you are not aware of it. You saw that when the subject of baptism came up and he brought it to your mind. That was not you being clever. That was him giving you the word at the right moment. He will do it again, often through simple things, not through a polished presentation.
Do not despise the small steps. Meeting new people, going even when it was hard, speaking one to one, listening in a group, these are real acts of obedience. They seem ordinary, but they are building a pattern of faithfulness. The mouth speaks out of the abundance of the heart. So instead of waiting until you feel a strong pull, ask God to fill your heart with such awe of him and such love for people that the words have something to overflow from. The spiritual things of God are not known by natural boldness. They are known by the Spirit. Ask him to take the gospel from your mind down into your heart until it becomes natural to speak of it.
With your mother and brother, do not first put pressure on yourself to approach strangers while they watch. Let them see you living as a believer. Speak about what Jesus is doing in you as naturally as you would speak about any real part of your life. That may be more difficult than talking to a stranger because their opinion of you matters more. But the same trust applies. Do not use their unbelief as an excuse to say nothing, and do not wait for a dramatic moment. A quiet word, a simple comment about what you have been reading, an honest answer when they ask how you are, can be seed sown over time. If God opens a door with a stranger while you are with them, take it. If not, be faithful in the ordinary conversation in front of you.
You already know the gospel. The barrier is not knowledge. Ask God to make you more aware of his love than of your own awkwardness. When you step into a conversation, you do not have to carry the whole weight of the outcome. Trust in the Lord makes you safe. The midwives did not know how their obedience would turn out, but they feared God and acted. You can do the same with a much simpler call: open your mouth for one small word, ask one question, tell one person what Jesus has done for you, and leave the rest to him.