What Causes Fluttering Feeling Inside The Stomach And Frequent Urination?

Hello, I m currently breast feeding my 6th month old, after giving birth I ve had a regular period, but it would always last 1-2 days. I was supposed to get my period 3 weeks ago, still have gotten it. Although during the time I was supposed to start, I had all the symptoms. I thought I would start so I waited and wait. Still nothing. So I took a first response pregnancy test. Negative. I took it the second pee of the day. Yet Im experiencing a weird fluttering feeling inside my stomach, I am super bloated, and have been peeing very fequently...