Need advice

I hope I’m in the right groups to be posting this. I am needing some advice. I know I might sound stupid to some so I hope comments are kept friendly. I’m 21, new to having sex. I don’t have much experience to tell you the truth. I was talking to this know I’ve known for ages and we decided to meet up, I told him this was my first time and everything went fine. During sex he asked if I came, or am cumming. I honestly didn’t know what to say, so I said I don’t know. Because that legit was the correct answer. Ladies, how do you know if you’ve came or not?