Aih, contractions memang macam perut keras & tight sampai sakit, then relax balik, usually starts dari depan perut tapi boleh spread ke belakang like you're saying, and normally comes in waves at regular intervals, whereas what you described (sakit then hilang after berak) sounds more like digestive cramps lah! A few of us went through the same at 36 weeks and panicked thinking it's labour, tapi once we passed motion it was gone. Since you're already 36 weeks and the pain came & went after using the loo, I'd say monitor it first, if the cramping comes back regularly in a pattern (like every 5-10 mins consistently), then better call your doc or go check in case, because everyone's labour feels different and it's always safer to get checked out rather than wonder! Your first delivery was quite different (waters broke without labour) so this time you won't really know until the real deal starts. All the best, mama!