Dont know if I have cum?

I’ve been with my husband for a few months now and am not sure if I have ever cum... people say I’ll know but dude I need to know what. I read online it said that I’ll shake and have a squirmy feeling which I have had those moments and they seem rare... and they seem to happen if I touch my clit rigorously for 5 min... and it gets all sensitive..

How come I Can’t cum when he penetrates me for 15 minutes??

I would like to orgasm.. can someone help me