Please help.

Hi, I have been trying to conceive for four months now. We've tracked my ovulation days. I am two months late on my period, so I took some pregnancy tests, all of them came out as negative. So about two weeks later, I started bleeding. Nothing heavy, just simple spotting. Which I found strange considering I usually start out with a very heavy flow. I thought it might be implantation bleeding. Could it be? I spotted light pink blood for two days, and on the third day, I had a very small amount of brown discharge and then the " bleeding " was over with. I get hot flashes quite often, I have a stronger sense of smell, and my nipples are very tender. Any insight ? Could I be pregnant?