30 Weeks Preggy-Difficulty in Breathing

I'm having a difficulty in breathing especially at night hanggang madaling araw, parang ang heavy ng feeling sa diaphragm part, as per my estimate nung una, mga 30 mins lang 3-4 mos palng ako nun, then now im on my 3rd tri tumatagal na sya 7 hrs the other day then kagabi naman 3 hrs. Is this due to exerted pressure of my uterus in the lungs?