High risk pregnancy. 12 weeks.

So It started saturday morning (yesterday) I went to the toilet and saw some brown spotting. I know Im critical from the start saw my baby on thursday was moving jumping and perfectly fine. Towards the evening the spotting got darker darker towards brown. We got worried we phoned my doctor at 20:00. He said dont waste any time and come right now. So we went, he took me In to my ultrasound the baby was there moving around and looked okay. But he said the baby is very very low down and that I have to take bed rest. He done me an injection to stop the bleeding. I am 12 weeks. I will be going for my big ultrasound on wednesday to the hospital. I am just terrified :( Anyone gone through this and had healthy pregnancy? Need advice :(