Open

It's about right after they have sex. And he is trying to hold on the the moment. She's fading asleep and he's asking her to stay open to the moment (and more completely open to the relationship) because they are in a moment of a natural spring of positive emotions.

I'm a fool for that shake in your thighs (woman's thighs shake during an orgasm) I'm a fool for that sound in your sighs (the sighs when both finish) I'm a fool for your belly (when a guy's backing out, her belly is right there) I'm a fool for you love (self explanatory)

He says, "I want to make this plain," so many times, it's clear that he can't make his emotions plain. He's trying to get her to stay with him so he can express himself, but she's falling asleep.

For a fun comparison, look at Kendrick Lamar's Poetic Justice. In it he asks, "If I told you that a flower bloomed in a dark room would you trust it?" asking if she trusts the fact that he feels closer to her right after sex. So they are talking about the same thing in different ways. In the end they are both pleading with their partners to understand but both he and Rhye have trouble expressing their emotions.