Implantation bleeding! Help!

So I'm supposed to start my period in 3 days. My first ovulation day was 11 days ago. We've been trying to conceive since January. Well I was nauseous and slightly dizzy last night and woke up feeling a little crampy and nauseous. When I do start my period, my cramps are rough. I can barely walk, I feel like vomiting, I'm in excruciating pain, and my periods are always very heavy the first day. Well today it's just light spotting and light cramps. Could it be implantation bleeding?