Period problem!

So I am on the contraceptive pill microgynon. I normally have a regular Period. I should have come on on Wednesday and finished today (Sunday). I have had pain, but different to period pain. I have bled a very small amount, a very light period mostly brown blood and a bit of red fresh blood. I normally have period pains for a couple of days but the pain is still here. It really doesn't feel right as normally so regular and predictable. Any ideas?