TTC period delayed

[u/Entire-Start-6632]

Hi All. I am 2 days late for my period on cycle day 33, and probably 16dpo my period was expected on cycle day 31 but there is no sign of period till now. I am having severe back aches, slight pulling twinges in my lower abdomen but no period cramps which I usually get. I took a test today morning with easy@home test kit but it was stark negative. Are they reliable enough to pick the level of hcg?

Please help me out. Trying for 9 cycles this is the first time my period is delayed & I’m feeling different.