Yes you can get some minor cramping especially during 28 weeks. It sound like your body is just adjusting to the baby and you are going to feel slight discomfort at time and thats because the baby is positioning its self. Now braxton hicks are going to be really close together. With my pregancy I had to have my Dr brake my water in order to get them starting. They feel like really bad cramps and are really close..... now if you start getting them now... count how far along they are... and if they are 3-5 minutes apart you should call your doctor or midwife but they have to be consistant not like the first 5 min then 10 then back to 5... trust me you'll now when you get them....