Last period was january, bad cramping, spotting an streaking for 2wks, upset tummy, sweating, feeling unwell, negitive pregnacy test what could it be?

Chemical pregnancy: It's really hard to say without more information but if your last period was in january, skipped a period in february and are now having an irregularly long menses in march, it's not impossible that you could've had a failing pregnancy in february that's now resolving itself. Nothing to be worried about unless you have severe pain/fever/bleed.