FPA Contraception

Help me!!

Right so, my periods have always been irregular, I had my son December last year, went straight into the contraceptive injection, hadn't had a period since being on it even when I had a break for like a month, well I've started to bleed, but it's pink blood, then a light red blood, then brown, then il stop bleeding for 30 mins and start In that cycle again, what could this be? Is it normal?