Implantation bleeding?

I have been spotting for a week straight. At first it was the very light pinkish color of spotting when I wiped. Now it's a darker redish color with pieces of stringy red blood. Is this normal? Is it implantation bleeding or something else? If anyone can help with advice I'd appreciate it.

BTW I've already taken 2 pregnancy tests and they were both negative. It may be too soon to test tho.