Need advice: Grounding Exercises Aren't Helping My Dissociation

I've been in therapy for nearly 10 years now and tried a ton of different approaches, as well as *many* different medications. It has been a struggle to get much of anywhere due to how much I dissociate. The most helpful therapy was EMDR, but eventually I hit a wall. I have previously done CBT, CPT, and have learned a bit of DBT skills. I am currently doing Internal Family Systems with my therapist and occasionally using Brain spotting on my better days where I'm more present (this is rare). We haven't completely ruled out that I may have a dissociative disorder, but she does not want to throw another diagnosis at me just yet. She said if anything, I could potentially have Depersonalization-Derealization Disorder.. All of that being said, I have absolutely no idea what to do. It has reached the point where I am unsure if I'm ever really present. Things have been very heavy for me lately and I feel extremely out of it majority of the time. I have tried a few somatic exercises on my own previously, but fear it could make things worse. It is severely affecting my ability to concentrate and do my school work. I have tried breathing exercises and other grounding exercises, as well as meditative activities.. but nothing seems to work. If it helps, it only lasts a couple seconds and I am then back to dissociating again. Any help, advice or suggestions would be appreciated!