Hi Brokensoul88,
I would have suggested the same as
@littlelostchild about having more time off work, but I understand you not wanting your parents to know.
As such I think you need to do two things -
a) Really work on grounding and stability. I think this needs to be a priority and you need to be disciplined about finding out about it and practising skills. This isn't pulling yourself together (which is a bit too much like self-criticism), but recognising that you have a big challenge and need skills to meet it.
I don't know what sort of therapy you're having but I wouldn't expect all of this to come from a therapist anyway. There are lots of resources here on the site (if you search on threads with "grounding" in the title) and elsewhere, and in the end it's down to us practising until the techniques become routine.
I would stress that it's not just things in reaction to being distressed, but also skills to use all the time to stay more stable. For example, regularly practising techniques that reinforce a feeling of groundedness (like consciously feeling your feet on the ground or orientating yourself in the present). Also, regular self-care techniques like deep breathing and relaxation exercises.
You say you're rubbish at grounding, but no-one is good at it until they've worked at it for a while. It's like building muscle/fitness/stamina at the gym - you need to just make a start, find out what to do and then keep working at it consistently.
b) You can ask for additional accommodations at work if you need them. Moving desks sounds good. You might also want to see if there are other things that would help.
I'm in the UK too. When I first recovered memories and started therapy I arranged for things like coming in late the morning after therapy because it was hard to get to sleep after, being able to take time out during the day and go into an empty meeting room or walk around outside to practise deep breathing and self-soothing, and other things. I made up the time by working longer hours at other times (which was also when the office was quieter). Only my line manager knew I had PTSD and he didn't know why. My colleagues just knew I "wasn't well" and was having to have some treatment that made me tired. I hinted that it was related to headaches, dizziness and back problems and this was accepted.
Good luck.