Worried I’m going to faint after PT

I don’t even know if I have POTS. My son is being evaluated for it and during that process one of his doctors noticed my hypermobility and informally evaluated me for hEDS and discovered I have it. When he asked me questions about greying out, dizzy spells, fainting, I realized what I have experienced is maybe not totally normal. I have only fainted 2x in my life. Once when I got very hot inside a church in Mexico as a teenager and once while I was having shower seggs with an ex. The second time was very scary because my boyfriend caught me and I came to. We both thought I was good so I sat up but then I fainted again and hit my head super hard and ended up needing stitches. It was very traumatizing for him as well because he had no idea what was happening. I grey out a lot of the time when I stand up fast. It’s not as bad if I wear my compression (I wear for lipedema). I am now seeing an amazing independent PT who is mostly doing soft tissue work on my thighs for lipedema/fibrosis. I lie supine or prone for most of the appointment. Today when I stood up from the table I greyed out so bad that I was sure I was going to faint. I didn’t say anything, which I know was stupid but I felt very vulnerable and embarrassed (and for some reason worried about freaking him out??). He knows about the hEDS and the history of fainting. I think I probably need to say something next time or like warn him somehow that this could happen, but I’m not sure what to say. Especially since I don’t even know for sure if I have POTS I am not sure how to phrase it. I also really don’t want him to fire me as a patient because he’s worried I’m a liability. The soft tissue work is LIFE CHANGING and I want to keep doing that.

Thoughts? (I am fully aware I am overthinking this so please do be kind.)