It may be worth getting your blood checked to make sure that your underactive thyroid is under control.
Suffering from depression, being under stress and anxiety can all affect the memory as well as lack of sleep and being dehydrated. Make sure that you drink plenty of water so as not to get dehydrated.
With the medication that you are on, I presume that you are not drinking any alcohol.
As you are in the UK and if you are still under the care of the neurologist, ask if they can do a scan of your brain and explain all the symptoms that you are having. If you are not under the neurologist any more, you will have to make an appointment to see your doctor and tell him all your symptoms. Write a list of all your symptoms before you see the doctor and give the doctor the list. Saves the hassle of trying to remember everything.
Ask the doctor if he can also refer you for counselling.
If you have unresolved underlying issues, you may require help with counselling to help you to deal or come to terms with those issues. You will still need to carry on with your antidepressants, but the doctor can prescribe a different one if you feel that the ones that you are on are not helping.
I would suggest you talk to your doctor about this, and if you aren't getting the answers you are looking for, get a new doctor who will listen.
A seizure that comes from an emotional center in the brain may be more likely to produce a change in mood.(This is from the Epilepsy Foundation site).
I would contact the doctor and go over everything and be honest about your symptoms. Best wishes. :-)
In addition, your meds may be contributing to depression if it is getting worse. Certainly, being hypothyroid will contribute to depression to some degree. You need to get the TSH under control. It does take quite a while to get the right amount of Synthroid so that your brain "catches up" with the thyroid. It sort of has to stop making too much TSH and realize you are getting it from your pills then you will go back down to normal. It took me almost a year to get to the right level and I feel so much better.