I've been ttc, & for the first time i've spotted twice this week. my period is due on the 27/12/2014. is this still break through bleeding ?

Most likely 'yes': Nearly 100% of mid-cycle bleeding is a form of breakthrough (uterine.) Cervical or vaginal bleeding is not breakthrough but also is not hormonal or cycle-related. Politely an respectfully, there is no such thing as "implantation bleeding." Bleeding - or not - bleeding between ovulation and your period tells you zero about whether you got pregnant. Good luck, though.