Guard down

I believe I created a wall around my heart from past hurt in relationships. Afraid of getting hurt and lied too so I build up a wall around my heart. Now I’m in a new relationship I believe my guard is up so high that it is affecting our relationship. He believes I’m not interested in him, I’m not genuine enough to care how he feels about stuff. It’s not that maybe my guard is up and I’m afraid to show my emotions and I’m shy also. How to let my my guard down some? Also how to become more genuine and affectionate towards him?