If she has a wall up and it’s obvious, it will take time. She has been very hurt before thus of course she does not want to feel that hurt again. Have patience and if you truly mean what you say, if you stick by her unlike people who haven’t to her in the past, she won’t be able to help but slowly let her guard down. Do not do this if you have ANY ill intentions. Patience 🙂
If you’re having so many doubts he is certainly not the one. I know it’s not what you want to hear but it’s true. Real pure love does not make you doubt. In fact, when it is healthy, true love, it does the complete opposite. It empowers you. Don’t settle.