Utovlan to stop my period?

Ok, mid October I got the contraceptive injection.. Didn't have a period at all until 7th of December, and it just hasn't stopped since, ( it's been 3 weeks today) I went to the doctors and explain it to them, he said it's very common to have a long period when you first have the injection, and he prescribed me utovlan, and told me the bleeding will stop if I take these, so for the past 5/6 days I've been taking 1 tablet 3 times a day and still no sign of my period stopping. It's driving me mad as it's mako me very tired and starting to effect my performance at work because of it. What advice do people have?