Hello Poppet
Sorry to hear you're having a tough time.
I would challenge your GP and ask for a proper assessment. My mum's GP told me that he couldn't do anything until she was a danger to herself or others. What utter tosh! I insisted we see a consultant (I didn't find this easy as by this time I was in a complete state), but I'm glad I did. Mum now has drop in care twice a day, an OT and I'm currently trying to get her a support worker.
Your MIL sounds like she is a lot further down the line than my mum, but even so, you can't and should not be expected to do it all on your own. The sons, and I'm going to be a tad blunt here, ought to get their fingers out. You really are doing as much as you can but you can't do it on your own. I know a lot of people go into denial. For sure, my brother has little input to my mum's care and as long as she picks up the phone when he calls, he assumes all is well. Mum says it's a man thing, but I don't agree. There are loads of lovely blokes on here caring for people.
Perhaps the fellas just don't realise how bad things are for you.
See if you can sit down with hubby and BIL and have yourself armed with some info off here. Perhaps when they realise how tough it all is for you they will become more involved in supporting your MIL and you. I know it's not easy, Poppet, but your MIL needs help from the professionals (as well as her family). She is lucky to have you as DIL, so don't feel guilty; you're doing as well as you can.
Please post back and let us know what your situation is. It's much better when you can talk to friends here on TP; I've found it a wonderful place.
With best wishes.
Crikey, I've just seen that Hazel suggests you show it to the sons ... hope they're/you are not offended by my remark!