Should I be bleeding?

I had my 2nd zoladex injection last week to suppress my ovaries. For the last two days I have been bleeding a bit, its not a full blown period but enough there to have to use a tampon. I thought with these injections you have a bleed after the first injection and then that is it, no period for 6 months. I was hanging on to the no period side effect, trying to make a positive out of so many negatives. Looks like I have lost my only positive! Thankfully I only have minor discomfort and not my usual period pains. I am still wondering whether I should be bleeding?