Hello and thank you for posting.

I'm afraid I don't know exactly what might be the reason for the blood and the thickened womb lining. But as you have had problems with bleeding and pelvic pains it is sensible to take biopsies during a hysteroscopy so they can get some answers.

One possible reason for womb thickening is a condition called endometrial hyperplasia, I have a posted a hospital trust information leaflet about it here for you to read .

Really until they have all their information back it is difficult to say what might be going on, but do keep an open mind. Waiting can inevitably be unsettling so try and keep yourself distracted and your mind busy to help time pass. 

Take care Tractia, and I hope you know more about what is going on soon. 

Sarah.