How do I win back his trust?

How do I earn someone’s trust back after hurting them a lot? My boyfriend and I almost broke up a few months ago because I did something terrible, and I have been trying my best to fix our relationship since then. He has forgiven me, and I know he still loves me a lot, but I am also convinced that it may take him a long time to trust me again. I know I did something bad, and I am ashamed of it, but I also know how much I love him and how much I want our relationship to work. I want to marry him and don’t know if that can happen if he doesn’t trust me. What should I do to try and get back to the way things were between us before all this happened?
You have to let your actions become louder than your words and accept that rebuilding trust takes time. To ask for forgiveness repeatedly won’t help because it has to be unconditional, and your boyfriend is probably still struggling with what has happened. It’s okay to accept this lack of trust too, if you can acknowledge that he has been hurt and may not see things from your perspective just yet. Spend as much time together as possible, tell him you’re willing to talk about anything even if it’s a difficult topic, and allow him to see that you care about him and this relationship. Time and communication alone can mend this state of distrust that currently exists.

I’m so nervous about meeting a guy I really like that I am afraid I will ruin our date. I want to come across as cool, calm, and collected. Should I be more aloof than I usually am?
Don’t overthink this. To try and be someone you’re not is usually the easiest way to send the wrong message. If you want this date to be successful, think about whether you would rather be accepted for the person you are, than someone you’re not.