That little heart beat feeling is hiccups and the Braxton hicks are pretty much what u described it feels like your bump is tightening and it goes away of u lay down or walk around :)
They feel like mild mild period cramps..and dont usually last long at all!
I've been feeling something like a heart beat once a day and I just thought that the baby had hic ups, so they aren't light pains then?
More like a heart beat or like bubbly feeling. You will know when your lil one gets them i just felt it for the first time 2 days ago and felt them again last night