Nearly 80% of all women are not capable of having an orgasm without clitoral stimulation. Intercourse without an extra hand or device usually can't stimulate the clitoris enough to be useful. If you're interested in an investement - there are a lot of items for couples that are meant to stimulate the clitoris which are easier (and less likely to lead to crushed fingers) than manual stimulation. Your local sex toy shop has helpful staff.