I'm a week late on my period

I'm usually a day or two late sometimes but I'm usually on time on my period and I have been right on time for a few months now. For some reason, now I'm late! I'm Not TTC. I just moved in with my boyfriend 3 weeks ago. I want to enjoy him and myself first, getting married, buy our first home before having or thinking or kids. I had 2 pregnancy test that were negative tho.