Am I pregnant? Seeking advise...

Archana
Hello, my periods are 4 days delayed. I had 1-2 drops spotting yesterday and very light bleeding today morning.generally my periods are 4 days long,1st 2 days heavy flow and next 2 days light flow.my pregnancy test is negative. Why I have light bleeding. Is it implantation bleeding. Shall I go to doctor for  blood test. Please advise.