Why is my boyfriend "scared" of getting married?

Hello! your opinions please😩 I have been dating my boyfriend for a little over 6 years. We are immensely in love with one another.He shows me in every way that he loves me and so do I. We don't live together but he spends the night once in a while. I have a 7 year old from my previous marriage that basically knows him as a father figure . 3 years ago We went through a rough time. I felt like our love wasn't as strong as it had started beacause we would argue for every little thing and I decided we needed a break,we seperated for 3 months and he begged me to get back with him (the full 3 months) He proposed and because I wanted him to prove to me he was ready I asked if we could just wait a couple more years to make sure That it was what we both really wanted. Everything has been great and We love and understand eachother more than ever. BUT, I have mentioned that I am now ready to take the next step and He stays quiet everytime i bring up the subject. He says we will get married but give him time.Should I just not worry about it as long as our relationship is fine?