super stressed

I need a bit of advice, I had sex on December 2nd and my ex & I used a condom (it didn't split) and my period came on the day it was supposed too. However, this month, I'm 6 days late. I've done a pregnancy test and it was negative, I just don't know what to do! I haven't had sex since and I'm really scared. If any of you ladies could give advice, I'd be greatful!