How do I know if I came? Or how to cum

I’ve been sexually active for over six months and have had a few partners since. I kinda feel like a late bloomer since I’m 20 and barely lost my virginity.

My current partner is fantastic, can make me shake, squirt and does everything I ask him to. He wants to make me cum but I don’t know how. It’s a bit frustrating. I don’t masterbate because I don’t feel safe in my house to do so and I’m still learning new things about my body.

I keep hearing about this explosion of feeling and ecstasy and I can’t say I’ve ever felt that.

Any help?