i keep getting period like pains but i just had my period

hi all,i had implanon removed on 29th dec 2010 as i wasn't very well while it was in,i had a period about 2 weeks after it was removed then i had a period in feb and a period on 24th march,then my next period wasnt until may 31st,then i have just had another on 5th july,as you can tell my periods are not very regular at the moment and the periods i had  were normal periods until the one i had in may which they  dont seem normal to me,the first day its really heavy and then just like a discharge for the next 4 days,i have just finished my period and now i'm getting aching and cramping like it is going to come back,this has been happening since may and i'm getting worried that there is something wrong