((((((((((Sweetlove))))))))))) You did a very good job with this issue!
Last year when my T took my insurance, they would only cover 10 sessions after the first 10 of the year. I was already going 2x a week as I was in burnout state from work. When I had my official total breakdown in Feb, I had to go on short term disability from work. As I was up to my eyebrows in heavy trauma healing work, my T had me come in 3-4 times a week! I was terrrified that there I was in the middle of the most aweful mess of my life and the insurance could at any time just "cut me off" and refuse to approve any more sessions.
All was fine for a little while, but then the insurance denied my visits. I was not yet done with my trauma work and it was only July and I had just sarted back to work after being off 3 months.
The entire time, my T told me to trust him - that he knew what to do with insurance in order to get me the help I had to have - what I NEEDED. I was not use to having an authority figure actually stand up FOR me! I was use to having to just stand up for myself while the adults turned and walked away from me when I told them about the horors going on at the hands of older children in the neighborhood or other adults. I had a VERY hard time trusting my T in this way and when I ran out of insurance, I thought "Well, this is it. Here we go again with being let down."
But in that session when T told me the insurance denied me, and T clearly saw my face change, T said "Do you mind if I handle this now - with you here?" ??? I was like "Sure!" And I sat back and watched him call the insurance. He was so firm with them! I had never seen that side of him!

He told them "I have a client here who is suicidal and has severe PTSD with dissociative identity disorder" (stuff the insurance already knew as he has to tell them my DX -- and I WAS very suicial at that time due to the heavy trauma work). He said "You WILL approve these sessions for my client." They put him on hold and transfered him to a manager. They told him they would "look into it" and he told them "No. I submitted this request two weeks ago and I need to see her TODAY. You are going to approve this for my client right now!"
They did :-) And they continued to approve his requests all the way through the end of the year regardless if I needed only 1x week or 2x week. And I was able to first hand witness and experience what it was like to have an authority figure STAND UP FOR ME!!!!!

This year he is not taking insurance, so that is good for me because I don't have to worry about the insurance thing.
Bottom line though, and the reason I wanted to share this with you, is because I wanted to give you hope in seeing that Ts can stand up to the insurance companies and they do have weight to push them into getting approvals. All you have to do is tell your T what you NEED - just like you did. ((My T made me do the same thing! I was the one who had to say "I think I need to see you more than 1x week" and T said "I think you do too, but that is up to you to tell me what you need from me."
So be 100% honest with your T about those needs. And allow yourself to trust T to do his job. It will work out. But I do understand the fear you are going through around this. Big hugs to you!!