Bleeding at 12weeks

So I’m 12 weeks pregnant with 3rd baby. I’ve been injecting blood thinners (clexane) twice as a day as I have multiple embolisms in my lungs. I’ve been experiencing slight bleeding past couple days. I went a&e where she examined and said my cervix was closed so can’t determine where bleeding is coming from. She did say it could be 2 things

1- it’s from the clexane which is causing the bleed as the blood is slightly on the brown side.

2- I’m having a threatened miscarriage

Just want to know if anyone has experienced this before? We’ve already set ourselves for the news that will be coming our way!