Increased fluid or amniotic fluid?

i am 27 weeks preg on my second child and have noticed the last few days the my underwear has been getting wet and sometimes my pants aswell. i've also noticed a white substance left on my underwear too i was wondering if i should be worried about it or is it normal.If im wearing white underwear i've noticed a brownish colour were the wetness is...i dont think its urine either as it doesnt smell like it and it happens trough out the day i dont feel like i need to pee or get a gushing feeling it just happens.... i've also noticed sometimes a greenish slimy discharge when i wipe other times it can be clear. any help or suggestions would be gratefully appreciated.