Horrible sex life!

My fiancé and I are having problems when it comes to sex. Luckily we're  not one of those couples who base their relationship on sex or we wouldn't be together. Everything else is great with us. We're deeply in love, and we do everything together. We rarely argue but when we do it's mostly b/c of sex. He's a problem with staying hard. It turns me off and makes me mad 😡. It's gotten so bad that he went out and brought stimulation pills from Walmart 😳. (Which didn't work) What can I do to make our sex life better. Any suggestions would be great!