Implantation Bleeding?

Hi, I last had my period May 28th, and have been thinking im preggers with really noticable size increase of my , sensitive ... ect... I had on June 4th, and 17th, I took a test thi spast sunday and yesterday, both negative. I also Had This past Saturday, so then i thought maybe i just conceived and it wouldnt show up yet. Well this am i gues i got my period.. but not sure... it was very light and pink. I put a pad on and now 3 hours later.. theres still nothing on the pad. I went to the bathroom again, and there was a bit but not since then. Usually my period is mively heavy from the start. I also am having lots of cramping and not feeling well. I cancelled my Dr appointment due to getting period but now im wondering if its really my period or implantation bleeding or something else???