Not letting people in

I suck so bad at letting people in and showing how much I truly care about them because I’m scared of getting hurt. My boyfriend doesn’t understand that I’m trying to let him in and we keep arguing because he doesn’t believe how deeply I feel about him. I want to start letting him in a show him how much I love him but I’m just so scared that he won’t even feel the same way which is just me going mad because he’s told me so many times. Do you have any advice on letting people in? Xx