1. "I believe in you"
This sexy position represents your trust in your partner.
2. "I am your protector"
Here the protector is her.
3. "I will back you"
It shows that your partner will back you either way.
4. "I trust you"
Here, the way the guy lies in bed shows that he will use any power he has to protect the girl. And the girl gives the message of "I trust you."
5. "I don't feel comfortable"
If your partner leaves a big space between you it means he/she is not comfortable with sleeping on the same bed.