13-14 dpo no period

I think I’m 13-14 dpo and I had a negative pregnancy test this morning with easy@home strip tests. Last night I had back cramps and this morning started very light spotting but it hasn’t increased at all or turned into a period flow. Has anyone had this happen? Did you start your period? Could I be implanting this late and still have a healthy pregnancy?

My follicular phase is highly variable so it’s possible ovulation could have been a day or 2 off but my luteal phase is always 13-14 days long.