Sayang, based on what you're describing, the on-off tightening that goes away on its own, the backache, and the irregular timing, it does sound more like Braxton Hicks, which is basically your uterus "practising" for the real thing. The key thing to watch is whether the contractions become regular, grow stronger and closer together, and don't go away when you change position or rest, that's more likely true labour. The mucus plug coming out is normal at this stage, though if you see any fresh bleeding or the pain becomes consistent every 5-10 minutes without letting up, please don't wait for tomorrow's appointment. Bagus sekali you're seeing your pakar esok, do mention everything, the tightening, the mucus, the sleep changes, semua sekali, and I'm quite sure the doctor will check your cervix and possibly do a CTG to give you a clearer picture. As always, your own pakar knows your history best, so trust whatever they advise after the examination ya, take care!