weird period

Ashley
My LO is 6 months old and I stopped breast feeding about 3-4 months ago. 
Lately my periods have been really weird, it's like we take a couple days to start up I have like pink or brown discharge and then it will slowly transition into red and I'll get cramps… But last time it lasted six days and rotated through Brown discharge and red blood for the direction of my period and this time I got light pink discharge then red blood mixed in with discharge and I'm still waiting for it to fully start, this has been a span of three days so far. My boobs are more sore around period time. I took pregnancy tests last period and they were all negative. Thank god. I haven't missed any of my birth control pills and we use condoms every time. Is it something to be worried about? Could it be my body getting back to normal still? Or the type of birth control I'm on? 
Help!