Masturbation

I’m not sure if i’m actually cumming. I masturbate by rubbing and using a vibrated but i’m still confused. I am quite young so I’m actually super confused. I feel something building up and it feels wonderful. But then it hits a point to where it just stops. There is a few seconds before it stops and I’m wondering if thats when I came? But when i watch porn they come and that’s the pleasurable part. The few seconds are great but then it’s just done. Can anyone please explain?