I'm freaking out!

Sarita • Pregnant with my 3rd. I have a 7 year old son and a 3 year old daughter 😊
I'm 16+4 weeks and I went to the bathroom this morning and there was blood in the toilet and when I wiped. It was dark brown, and my back hurts and I'm crampy. Has anyone else had this and everything ended up okay? This is my 3rd pregnancy and I've never ever bled before. I'm so scared!