Developing Symptoms after 20w

Has anyone else had pregnancies where they had little to no symptoms and then suddenly at the halfway point the pain started to kick in?
Right now I'm 20w and 3d and I can feel the baby pushing on my bladder even more than before, it's more defined now. I've only gained a total of 6 pounds but it's very painful. And at night I have terrible leg cramps even though I get enough excersice, sleep, and vitamins.
Anything similar ladies?