Knackeredmother - I so understand how you feel. When PFB DS1 was diagnosed with aplastic anaemia aged 3.5, and my twins were 1.5, we received very little help from our families. He had to stay (thankfully only) four weeks in an isolation cubicle in GOSH after chemo and bone marrow transplant, followed by a year of immunotherapy and enforced imprisonment in the house, to avoid the germs liberally spread around by people who don't realise the implications of sharing their chicken pox etc. etc. During that time, we needed any help we could get and I became very bitter indeed that DH's family, all of whom had late teenage children, did absolutely NOTHING to help, even though they all live within 10 miles of us (he had two older brothers and an older sister). My family, such as it was, tried their best, but my mother's idea of 'helping' was to split the twins up, my sister lives 100 miles away and already had her hands full with an epileptic 10-year old needing brain surgery and a toddler, but at least she offered to have the twins, which was much appreciated, although I couldn't bear the thought of the whole family being apart. So very luckily for me, a wonderful friend, who had three DC of her own, then aged 6, 4 and 1, took the twins while DS was in hospital, enabling DH to carry on working and to swap with me at the weekends so I had a break from the hospital, and got to see the twins. What a great friend, and a wonderful thing to do for us. I was disgusted with DH's family and have had nothing to do with them since; as far as I'm concerned you can choose your friends but not your family.
You will look back on your hour of need and be proud that you got through it, but you need to accept that some people are fundamentally selfish, whether they are your family or not, and others would help you even though they are not related to you. I was bitter for a long time, but it is a pointless and negative emotion, try to conserve your energy for your DC and DH as much as possible, and well done for keeping working too, that must be really hard, at least for me I didn't have to try to hold a job down at the time.
Good luck, hope things get better for you 