Should I get a blood test?

All this week I have been crazy emotional and I get pissed at the smallest things I usually wouldn't. I've had a decrease in my appetite and have lost almost 10 pounds since monday (I usually have a really had time losing weight and can't even lose that in a month!) I have had cramps for a week+ and usually I don't really have cramps pre period. My period was due to start Thursday. It is usually REALLY heavy and I go thru 5-6 pads a day. Well Wednesday I started spotting and it started light pink but then turned to red. I stopped yesterday and I usually go 5-7 days. I've taken a few tests (first response) and have come back negative. Was it my period or implantation bleeding? Is it too early for urine test to detect the hcg hormone? Should I go get a blood test? Please help!