Bfn day 1 of missed period

I’m not sure what to think as I’m fairly new to all of this. We are in our first year of ttc, I haven’t missed a single period up until today! I was due to get my period this morning but absolutely nothing, I usually get cramps leading up to my period and I haven’t had those either! So my first thought was that I may be pregnant this time, I took a test and no second line :(

I will try once more in the morning but I don’t think I’ll get my bfp overnight…

My question is could I still test positive in a few days or am I out this month as my period was due today? I thought that I would have definitely got my positive today if I was pregnant?

Thanks in advance!!