New comittements

Tinabean16 
I'm really sorry to hear this. If the tribunal decision is that you are fit for work, your sick notes are still relevant, because (as your work coach has said) you have got worse. That means that whatever the tribunal decision was, you are worse now, and so you can ask to be sent to another work capability assessment. Probably not what you want, I know - but if your work coach agrees that there has been a change (they can hardly deny that as they've said it's what your fit note says!) & you've got worse, then I would use this to be reassessed and hopefully, get a correct outcome.

I would argue that there has been a relevant change of circumstances (you've got worse), you've got evidence of this in your fit note, and so what the work coach should be doing to support you is to refer you for a further work capability assessment (that will involve a new UC50 and could involve another face to face assessment, but it doesn't always).

Also because you've got worse, your work coach can suspend your work search requirements and agree that you don't have to look for work. For the first 14 days of your new (worsened) sick note, they have to do this. After the first 14 days, they don't have to do this, but they certainly can - and arguably they should, if the fit note says you shouldn't be having the stress of job search.

Even if they don't suspend your work search requirements completely, they can decide that you don't have to look for full-time work. I think your 'expected hours' (of work & work search) should be lower because of your mental health problems. I also think that if the Jobcentre don't agree to support you properly, they could be in breach of the Equality Act 2010.
This extract from DWP full service guidance for UC may be helpful:

'work related requirements should be reasonable and tailored to reflect any restrictions including, hours, type and location of work, which are appropriate to the claimant’s condition. The fit note may help tailoring requirements. If the claimant provides new medical evidence which supports either of the following:  a condition that is different from the one on which the WCA decision was made  a deterioration in the existing condition The claimant re-joins the health journey and Day 1 conditionality applies. Refer to Work capability assessment outcomes.'

In other words, as you have a deterioration, you should be treated as if you were presenting fit notes for the first time. You shouldn't have any work-related requirements for 14 days, and beyond that it is up to the work coach. Meanwhile, they should be referring you to a new WCA.

Meanwhile, it sounds as if you could really do with some support to help you with your next steps. I wondered if there was a Citizens Advice or another disability advice organisation who might be able to help you? Or as your GP sounds as if they are trying to be helpful, they might know of an advocacy organisation who can help. It's so difficult to negotiate with a work coach all by yourself. 

I hope this helps.

Will