“Can I give up my birthright?”

Can we give up our birthright (our salvation)? If not, then why does Hebrews 12 mention Esau giving up his? What does God canceling “the certificate of debt” mean in Colossians 2? I feel like the Lord asked me to do a bunch of things that I wasn’t willing to do. Then I rebelled and married a man who may be an unbeliever. Now I have a child with him. I’m not sure if I’m supposed to try to go back to my old life. Can you help?