I've been there, where you finally let your T in, your walls crumble and they see your vulnerable insecurities, you tell them things you'd swore you never tell anyone. You really feel like you made great progress and had a breakthrough and did some good work, however the next sessions are nothing like that and it's like you retreated back into your castle and are back at a somewhat square one.

That I have found through the help of PC and my ex-C, is normal. A lot of times it is either a combination of your T wanting to pace you and give you time to recover instead of harming you by bringing it all out at once, or your own defences trying to heal you, which is perfectly normal. This does not mean you won't ever get back to that spot with your T, you will. It sounds like you have quite the journey ahead of you, just know you're on the right track!