should I expect a miscarriage? please read I'm so confused and sad here

So I am 15+4. Thrusday I gushed bright red blood for 5 hours. And than it stopped and spotted brown for 2 days. And than this morning started bleeding bright red again for 2.5 hours and now again back to brown spotting. I've had 4 ultrasound done, 2 internal pelvic exams, had my cervix checked and felt 5 times, placenta checked, baby heart rate good 148-160 today... said everything with the baby is looking good but cannot tell me why I am bleeding and called threatened miscarriage. I'm  terrified not knowing if I will lose this baby. If I were going to lose here would it of happened by now? Since the bleeding comes and than stops? I don't know what to expect or what to do.