Could I be pregnant ?

I have 25-26 day cycles and it’s like clockwork. My period was supposed to start on the 5th of this month. 15 dpo today n I’ve been spotting since the 5th which makes 3 days now and it started around 6pm when it usually starts in the AM. I usually get horrible cramps with decent sized clots. I’m barely filling a pad now and the clots are tiny like nerds only when I wipe, I’m mid cycle it should be way heavier by now. Took a test this morning and it was negative.