How can I stop being insecure in my relationship?

Personally, I feel like communication is the key. At any point, if you feel insecure about anything in your relationship, be it that of friends or a romantic one, I believe you should feel free to ask the person regarding any doubts you have. I have recently started doing that, starting with - hey this may feel random/ hey just had a question or whatever works with you. If the other person is a good friend/partner, they will have no problems in this form of healthy communication. This will slowly lead to trust which will gradually wash away your insecurity. It has helped me and it may help you too :) Have a good day :)