31 weeks yellow discharge!

Ive been having thick yellow discharge since i was like 4 months.. Its gotten worse since I turned 27 weeks.. I've gotten checked for an infection 3 times and i don't have one! I have to wear a pad because it sokes my panties.. The weird thing about it it that it looks watery and white on my underwear, but then when i wipe, its yellow! im carrying super low and baby is big.. I feel lots of presure and have alot of braxton hicks.. Does anyone know if this is normal??