I'm bleeding, one minute its heavy and then the next its light could it be implantation?

Hi my name is Ju i had my period on Jan. 24 and it was normal. But i was due for my period Feb.21, i started bleeding 3 days later and it started off really light like a brownish pink then it started to get heavy,  it fades away and comes back again. It keeps fluctuating from heavy to light now. I had light cramps at the start.I cramped for the first day or so . Sometimes it just feels like gas that's making my stomach feel full. My periods are pretty good at coming on time but i'm very concerned with this bleeding because it doesn't feel like a normal period at all. It doesn't even feel like i'm bleeding, like it would if i was on my period. Only when i go to the bathroom i notice it. There are some clots that are in the blood at times. I've also noticed alot of changes in my body that have not been there before. The veins in my body such as the hands feet and breast are prominent and very visible, around the areolas and they are starting to darken, and my breast are very tender, and usually you hear about women's breasts becoming tender before their period , but that has never happened to me. I had sex over a month ago and i'm not sure if this is just my period or could it be implantation? If anyone could tell me anything that would be helpful, i would appreciate the insight and what i should do .