I was on 150mg when I stopped due to persistent weight gain.
My doctors had assured me I wasn't going to gain weight on Sertraline (it was partially medicating my eating disorder), the practice I was with first insisted on annual updates via telephone conversation before allowing the pharmacy to dispense my monthly amount, then didn't bother with those anymore after Covid and at some point I realised I had gained 4 stone and my doctors weren't interested and would only berate me for the weight gain. I had also felt a lot better for a long time.
I halved my tablets at first, then started taking half only every other day (it takes 3 days for the medication to fully leave the body), then stopped over the course of about 3 months. My weight gain stopped.
Was it safe to do it without medical help? No, but good luck trying to get a suitable appointment, even on the phone, when you can only answer at specific times.
Having said all that, OP, there will have been a reason for upping your medication level in the first place, and the fact that you are still experiencing huge anxiety attacks point to you still needing something. Sertraline took 2 weeks in my body every time before I was stable on a new dose and you may just need to give it more time.
Please do NOT mix St John's Wort with sertraline. I am sure I recall it was on the "don't" list in the leaflet and in any case, you'd have to check interactions with your pharmacist at the very least.