Not sure if i should go to ER...

Journey💕11-9-16
I am 18 weeks pregnant and since last night i have been having horrible pressure on my vagina and butthole. It hurts to walk or even shift in the bed. Just now when I went to pee I had clear/kinda milky colored discharge... I have a history of preterm labor. Is this worth going to the er? I feel like I'm always at the er for every little thing...