How to improve our sex life???

So I’ve been married 12 yrs., 3 kids etc... my husband and I have always struggled with our sex life. I was very sexually active before we met. I was with the father of my first child for about 3 yrs and sex was great but he was jealous and abusive... so I left the relationship and later met my husband. He suffered from insecurities when it came to sex but I fell in Love 😍 I thought things would change after we got married... but here we are 12 yrs later and we hardly have sex... he’s an early cummer- if that’s a word. We would love another child but I think his sperm count is low 😳 how can I help him without hurting his feelings... and what can I do to stay motivated??? Sometimes I would rather not even try to avoid getting disappointed... not trying to be mean. So that’s why I’m asking for advice 🙏🏼