I will be 36 weeks pregnant Friday and I' having cramping,Lower back pain and more discharge than usual!?

I will be 36 weeks pregnant Friday and I' having cramping,Lower back pain and more discharge than usual. I am very uncomfortable, I woke up this morning on my left side and I was cramping periodically. The back pain started a little bit later this morning. I have High blood pressure as well, And I'm on meds for that.I've also had sudden swelling in my feet the last 2 days. I don't usually wake up with swollen feet its usually by the end of the day when they swell. I have felt awful lately. I have a doctors appointment Friday its a scheduled sonogram.Should I wait till then if I don't start having strong contractions? What is going on with me anybody know from experience?? Well I just don't want to call my doctor if its nothing. Well thanks everybody in advance. Please help me!!