Do you think this could be a baby?

Hey,

Im having some problem. Im not sure if im pregnant or not.
I have irregular period, and havent had one since feb. I took a pregnacy test about two weeks ago.it was negative.

But me & my boyfriend had unprotected sex. the 22, 25, 27 & 29 of March.
My last period in feb was on the 20th.

Well yesterday i noticed that when i went to the washroom there was little blood, it was a brown color and only appeared when i wiped. Im hoping its implantaion bleeding. Just now i dont know when i should test again. I took one yesterday morning, but that was before the bleeding, and it was negatvie.