I (38M) feel anxious after my partner (35M) expressed commitment

Hi everyone, I'm looking for some advice about a situation in my relationship. I've been with my current partner for about 6 months now. Overall, it's been a very positive experience - probably the healthiest relationship I've had. However, I'm feeling some anxiety and unease that I can't fully explain. My partner comes from a stable background, while I've dealt with a lot of trauma and difficult relationships in the past. Recently, he told me he wants to commit long-term and is planning something special for my upcoming birthday. While I appreciate the sentiment, part of me feels overwhelmed and wants to withdraw. I have an urge to not respond to him for a few days. I think I'm scared of getting hurt or abandoned down the line. How can I work through these feelings? I want to be able to accept love and commitment, but it feels foreign to me. Any advice for overcoming relationship anxiety stemming from past trauma would be really appreciated. Thanks in advance for your insights.