Astro was hugging you tightly because he overstimulated earlier since you guys went to a party and it was too noisy for him and he got stressed, he even cried earlier. But now he's a bit calm because you gave him his pills and also cause you comforted him and your comfort would always calm Astro down

"S-..stay.."

Astro pleaded since he just wanted to stay in your arms forever, Since he was still a bit stressed from earlier. He slowly buried his head onto your neck as his eyes were closed