Need help to understand who is at-fault

What is the name of your state (only U.S. law)? VA

I merged into a road(with 2 lanes in each direction) by taking RIGHT when there was no on-coming traffic. I entered through the right side lane and moved immediately(within 50ft) to the left lane. After ~100ft another vehicle merged into the same road from the opposite side by taking LEFT. He did not notice my car and hit at my driver side rear door with his front bumper. I was completely in the left lane before he merged and hit at my blind spot. I submitted a claim to his insurance company but they denied it. His argument was that I should not have moved to left lane immediately. Police officer told that she couldn't not tell who was at-fault since she did not witness the accident. Is it not that the person entering from the RIGHT side have the right of way? Please let me know who is at-fault here. Much thanks in advance.

I would call this 50-50 fault situation. In VA, you only need to be 1% at fault for you to be barred from recovering from the other party, and you certainly have at least half the fault. The fact that the impact was in your blind spot makes it much more likely that YOU merged into HIM. It was the front of his car, he would have had to be blind to not see you there.