This is how it usually goes.
My girlfriend is petite, I am relatively tall. We have to use lube to get me inside. When I have succeeded to push inside bit by bit, she holds me with her arms, it’s so tight and snug. She isn’t very loud, she holds her breath while I push in and moans almost silently and submissively when her small pussy is filled out by my length. I thrust and it feels like a key turning in a lock. It feels so overwhelmingly good, so warm and tight, I thrust 5 times, her pussy squeezes me and I need to cum, I have to cum my body tells me with euphoria. It feels so natural and so insanely rewarding. After 10 thrusts I ejaculate inside her, I insert deeply and cannot move because it is so intense. We stay still for a moment like this before I pull out.
I think it is some animalistic instinct to get her pregnant that turns me into auto-mode to orgasm. I don’t even try to stop it – and I couldn’t anyway.