Does Implantation Cause Vaginal Bleeding?

i dont get my period. its very irregular. and the doctor also said it would be hard for me to get pregnant because i dont have enough thyriods.but me and my boyfriend have been trying re3cently to get pregnant . (08/07/2011) now i have weird cramps and my breasts feel sore and quite swollen, on the 29 i had light pink blood but only when i wiped .2 days later when i woke which is today i had light pink but also with eiter clear or white discharges. i'm 20 years . i'm not sure if it's implantation bleeding or my periods really coming back . i'm more confused. please help. p.s. we do want to be pregnant .