OK me and my husband had unprotected sex on the 13th I was due to start my period on the 15th but didn't start until the 18th and currently still on it is there a chance I could be pregnant

Let's see - you had unprotected sex, THEN you got your period, you STILL have your period and you wonder if you're pregnant.

Most probably, no. In fact, almost definitely no.

There are times when women have what they think is their period during pregnancy, but the fact is, you had sex during a time that wouldn't be the normal fertile time for a woman, and you do have your period.

Very unlikely that you're pregnant.