Yes it can. Hormones are the driving force behind milk production. Changes in hormone levels cause changes in quantity of milk produced. My period is still fairly irregular right now while I'm still BF, so it may not be pg, but I'd test just to make sure.
If you are not wanting to get pg right now there are some non-hormonal ways to prevent it. I had a Paragard IUD implanted after Kate. I honestly don't know if they are available in the UK, but it might be something to check into.