Preterm labor or normal please help!!!! 32 weeks?

im having constatnt lower back pain lots of braxton hicks i think thats wht they are im not sure though but im having one at least every 10 to fifteen minutes they are lasting 30 to 45 seconds they do not hurt but they are a little uncomfortable i dont know if this is relevant but i did hav a bowl movement a little while ago it was green soft and mucusy me and my husband had sex about an hour before my back started hurting ive tried walking it off i took a bath and am now keeping track of my contractions should i call the birth center or am i just over think things my discharge hasnt changed at all i did eat quite a bit of salty foods today idk if that helps at all but i have drank two 1.5 litter watter bottles