Advice

So I woke up on Thursday with a light brown dot of blood on my toilet paper just once. I called doctor she made me go in for blood work to check hcg and wanted me to repeat blood work this morning. My doctor called and my hcg levels on Thursday were 5,857.30 and today my levels are 5,898.90 so they went up my 41. My doctor called me and told me I will have to go for ultrasound on Monday because this is not a good sign. I have been crying all day and don’t know what to think. I don’t want to loose my baby. Has anyone been through this before.