Help I'm freaking out

I'm 5 weeks 6day, last night I had major cramping in my pelvic area and back pain with it. It last quite some time and finally after having a BM the pain subsided. Well today I havent had any pain just pressure like I need to go #2 but I cant, when I pee I have light brown discharge or spotting on the paper when I wipe. I have called my doctor but havent gotten a call back yet. Please someone tell me I'm not losing this baby. 😥😥 ultrasound scheduled for monday