3 days late

So me and my boyfriend uses the withdrawal method and we've used it for years , our last time having sex when he pulled out he barely made it all the way out ... Afterwards I had a weird feeling but I ignored it because I mean we've did it for years and it's been fine right? But I have been stressing about possibly being pregnant since the last time ... & now I'm 3 days late on my period... Could I be pregnant ? Should I worry yet ?