Contraceptive pill?

i've been on the pill for about a year now and have had no problems apart from when i started on them i had abit of breakthrough bleeding for 2-3 months ut that went and the doctor tod me it was normal. the last 2 months i've been bleeding about 7 days in to my new pack of pills after i've had the 7day break for the withdrawal bleed. i'm really confused about why this is happening is there something wrong?