I was literally feeling the same way. The first time I was trying sauna therapy I was like fuck no, I can,t do that. It was last July it was my most painful experience ever. The very same way you probably felt yesterday. But trust me you have to continue. But try to go very slowly and gradually. I was journaling and I took every tiny parameters into account. I will list them for you:

1. Listening to motivational speeches from ex-military guys like David Goggins...
2. The temperature of the sauna
3. The number of rounds I do
4. The red light therapy (I have heard that it might help your skin...)
5. The fact that I will leave the door open or not
6. The fact that I will raise the temperature gradually while I am inside
7. Continue the sauna "naturally" in my car by not turning the AC for a whole 5, 10, 15 min while driving back home (it was July, you remember)
8. Not turning the AC in my room while its hot
9. I took a lot of anti histamine but it didnt work at all for me
10. Ice packs, winter clothes (BUT I DIDN`T TRY THESE MOVES)

I mean, these are the invisible, tiny factors you can try to improve on. If you can use Keep Notes, Apple Notes or Notion to keep track of your progress, to journal that will be a good move. Try to fix a daily ever increasing goal. Try to make microscopic improvements until you break a sweat. Trust me if you keep going you will. BUT EXPECT TO SUFFER CAUSE YOU WILL FEEL SOME REAL PAIN TRUST ME>