Orgasm??

I’m able to orgasm by myself when I masterbate easy but when it comes to sex idk if I can cum like I feel like I’m about to but than the feeling goes away it’s hard I’ve only ever orgasmed once while being fucked and it was weird cause I was touching myself while he was fucking me and I orgasmed but the orgasm felt like I didn’t even orgasm like the feeling went away.

So Do I orgasm or not when I have sex??