Why can I not have an orgasm?

My boyfriend has been trying so hard but i can never seemto have an orgasm when we have sex. Last night he gave me head and fingered me . It felt nice & i got really wet- but I just could not cum. I don’t understand why? I have not had an orgasm in at least 3 years. I can tell my boyfriend feels bad , although I don’t make out like it’s a problem...

Can anyone help,