Cd 25, thoughts?

I am on cycle day 25

Not really sure when I ovulated

But

Yesterday the worst back pain I ever felt started

Middle back crazy pain just sore without having done any activity to injure myself

Tested this morning a bfn

Last night and today I feel a pin pricking sensation repeatedly, happens every few minutes in the same spot

Lower left groin region

Could that be implantation signs?

Would I have had Even a vfl?

Still time for a bfp?

Period due around October 4th