Pregnancy does a lot of things to a woman's body and I wouldn't be concerned as long as there are no other symptoms, no pain, or any other physical symptoms that would indicate a problem. Just enjoy the blessing of a light period as long as it lasts. Most likely it will eventually come back as your hormones regulate, but it could be years, if you are lucky. When I was pregnant with my first child, I shrunk an inch and my feet grew a size lol. And I never got those back of course. I agree with the post that advised against mentioning to your gyn. All they will do is put you on artificial hormones that affect you and your baby, despite what they tell you. They are in the business to give you drugs, plain and simple. Just use your own judgement and intuition, it usually is right.