umm a little concerned on being late with my period

Umm I'm like 7 days late from my period ... I've never had sex and the last time I was close to doing stuff with a guy was like 3 weeeks ago but nothing happened..... I'm usually never late but I don't know I've been feeling sick off and on lately ...should I be concerned a lot ? I've had a this happen before but I was much younger and had no interaction with guys lol