What Causes Delayed Periods,cramps And Sickness After A Depo Shot?

hi i had my first depo injection 4 weeks 6 days ago and i still havent got my period yet, ive had no bleading at all just stomach and back cramps, feeling sick,, really hormonal, needing a wee alott and being tired all the time. i had the depo injection years ago and i bled frequently for the first 6 months then i cam off of it to loose weight now i just have no period at all, is this normal