Help me please

Hi! I'm 22 years old .I need some help and advice! I was due my period on the april 7th. On may 1 I had cramps and every other period signs (emotions, bloatedness, spots etc). On the may16th I got my period and I got it very heavy and very clotted and it went through to 17. This morning (18th)I woke up and I had an spotting brown of blood on my pad. Today 19 I have a mega sore back, gassy and very bloated so I took a tests and it was negative not with the 1 urine in the morning. Please help me if yoy can!!! I'm not sure what to do.