What Causes Vaginal Bleeding After Taking Contraceptive Pill?

ive always used microgynon 30 as my contraceptive pill for 10 years, they have just moved me to levest 150/30, im told this is just different packaging? However i started taking the pill again as usual on monday after my period.. but i started bleeding again on the wednesday night and still havent stopped. ive never had bleeding outside of my gap week. is this normal? i started using tampons for the first time on my last period. will this have anything to do with it also?