28 weeks tomorrow and worried

So this is my second baby, and the past 18 hours I've been having what feel like period (lower) back pains/cramps. With my first baby, I didn't feel the tightening of my belly kind of contractions, it was ALL in my back. My boobs have also been leaking the past 3 days, like have to change my shirt (if I'm not wearing a bra) or have to change my bra because they are leaking so much. I have been drinking nothing but water also.. I also met with my OB on Friday for a routine checkup and tried telling him about this pressure pain I've been getting "down there". To explain it the best way I can, its like something is jamming into my pelvic bone- the baby also always kicks me lower than my underwear line and my belly is ALL low. He didn't seem to concerned about that either.. I know I need to call my ob about the back pains but their office is not open today.. thanks for any advice in advance and for reading through this if you stuck around through my confusing-ness.