So has this happened to you?

I have been lactating for 3 months now. I went to the doctor and had blood test to see my prolactin levels. I had an ultrasound d done on my breastfeeding and everything came back normal. Now that being said my last 3 periods have been short. I usually have them 7+days and they were 3-4 days long. I am still lactating and I for the life of me have been feeling flutters and movement. They did not do a pregnancy test when they did the blood work. Am I going nuts?