Susah nafas malam-malam at 26 weeks tu memang common, but the fact you're asking means it's bothering you lah, a few of my mum friends had this during pregnancy and a couple ended up checking with their doctor just to be safe. It could be the baby pushing up on your diaphragm or hormones juggling your breathing, but since you're asking seriously, I think it's worth mentioning to your doctor at your next checkup or call them if it's really bad or comes with chest pain. Try sleeping with an extra pillow under your head and shoulders to help you sit up a bit, and see if that makes it easier malam-malam!