How do you know if you're cumming?

Belle
I'm in a relatively new relationship and it's also my  first. My boyfriend and I lost our virginity to each other. With this said, I have no idea how to or if I have came while having sex with him. I don't really know what I'm supposed to feel. I mean, I think he's really good. I just don't know anything yet. Does anyone have any knowledge to help enlighten me?