Okay, breathe. You are not the first person in this position and you won't be the last. You're evidently intending to plead guilty and you have quite a lot of mitigation. You can look at the sentencing guidelines here if you want to look / can bring yourself to. I'm assuming fraud not theft if the maximum is 10 years.
The sentencing guidelines on fraud at a worst case scenario would have you at "high culpability A" because it was over a sustained period of time (better case scenario would be "medium B" but let's go with worst case scenario for now).
Harm caused would be category 3, between £20k - £100k, and the starting point is based on £50k. You might not have stopped if you hadn't been caught, so let's call the intended harm £50k and take that starting point. Lesser impact to the victim who is not an individual.
Starting point for an A3 offence is 3 years, with a category range of 18 months to 4 years.
None of the statutory aggravating factors seem to apply from what you've said (would need to know more).
Lots of the mitigating factors do - remorse, no previous, sole carer for children, co-operated with investigation, early admissions, difficult background as you were in the care system, prospects of being in work high.
Then a third off for an early guilty plea.
I think you would have a strong chance of it being 2 years or less, at which point the court is obliged to consider whether to suspend the sentence. If it is suspended you don't go to prison unless you commit a further offence during the period it is suspended, in which case the suspended sentence is activated AND you are sentenced for the new offence.
My best guess would be that you are looking at 18 months - 2 years suspended with a hefty unpaid work / rehabilitation requirement. Please stay connected to your GP and if you possibly can, make repayments. Good luck.