Why can i get an erection but not ejaculate?

Depends: Are you having an orgasm and not ejaculating?

No ejaculation?: If this is a frequent issue, see your primary care MD for a referral to a urologist to check on your male hormone levels. Otherwise, anxiety over performance in sexual situations may impose a psychological inhibition of ejaculation in certain sexual situations. If prior sexual experiences were normal, this is probably treatable.