Advice needed asap

Hi, I;m 55 and have suffered with severe anxiety, depression and panic for years, became worse when I was diagnosed with breast cancer 11years ago, fortunately I am in remission.
I changed my job ( nursery nurse ) in October 2013 to take up a position in a care home as a housekeeper, this didn't work out for me and consequently I was off sick with my anxiety and depression for 3 months, left that job and got one with a childminder, that's was great at first, now has become unbearable, 10 hour shifts with no break, holiday pay is illegal ( will only pay max., of 3 hours a day holiday pay ) she has been told about this but says "she can't afford to pay ".

My mum who is 79, is not in good health so trying to help her too.

Its got that the last few weeks my anxiety and depression are really bad, my marriage is now beginning to suffer as well as my everyday life, have little or no interest in anything.

I have been diagnosed with Affective Disorder, I take Citalopram, Diazepam and Zolpidem.

I have continued to drag myself to work so far, but to be honest, now feel completely drained and not in a good place at all (not suicidal)......

I am considering self certing., for 7 days as I have a Dr apt., on 8th July.
Just wondering, would this just be "giving in" to my condition or justifiable ???

I've been here before, and I really don't like it, my chest is heavy, palpitations etc., I feel so stressed, sad, anxious !