Why am I so passive ??? 🥵

I always put myself under stress because I can't say no! So i met this guy online and we exchanged numbers and he wanted to meet me, He just keeps pressuring me but i have low self esteem so i kept backing out, but he is very persistent finally i met him 2 weeks ago, and ever since he had been pressuring me to see him. He is very nice otherwise i feel bad when i say No for i might disappoint him.
But i showed up last time but I'm not ready for a relationship... i used every excuse in the books to let him down gently. Should i block him???