My husband accidentally ejaculated inside of me on day 7 of cycle. my period is normal, usually ovulate day 14 or 15. am i safe or should i take planb?

Depends: Pregnancy has been reported from exposure on any day of the cycle.Your regularity decreases that risk, but it remains. Since the sperm can remain viable for several days in your genital tract, your timing is cutting it very close.I would consider it a real exposure.

Plan B: Assuming you use the "withdrawal" method, I recommend using Plan B to be as sure as possible that you don't get pregnant. While the ovum (egg) stays viable for only about 24 hours, sperm are much hardier. We know that they can remain viable for at least three days inside your reproductive tract. Even though the likelihood is small, they might still be waiting there when you ovulate.

Small risk: it is possible for you to be pregnant but unlikely. sperms generally live 3-4 days and eggs ~24hrs but it is possible for sperm to live up to 7 days under ideal conditions but again unlikely

How worried are you?: Unprotected sex is unprotected sex; which means you could perfectly well get pregnant, though the chances are less with this timing. If you really don't want to be pregnant you need to take the ECP, if you are willing to chance it the risk is likely low. Unprotected sex is never guaranteed safe.