Dear Elaine,
Welcome to TP. I'm sure you'll find a wealth of support and information here. None of us is an expert, but we are Carers and we all have our own stories, triumphs, tragedies and burdens to share. I could not imagine taking this journey without TP - it is my absolute life saver!
It doesn't seem fair that the burden of responsibility lies on you. Is this something you want to do alone or are your siblings just "absent" from their responsibilities?? (You might find the Siblings thread interesting!!)
Perhaps you could ask your GP to ask your Dad to go in for a "regular check up" - particularly if he hasn't ad one for a while? Some people on TP have been successful in persuading a parent or partner to see the doctor by saying they need an "over 65s" check - I guess you could adapt this little fib to suit your Dad's age!!
If you work in a Care Home you probably don't need anyone to tell you that fibbing is sometimes the only way forward with Dementia sufferers. As relatives (spouses, partners, children, grandchildren, etc.) we find this very hard to do - but it seems essential at times.
Wishing you the best of luck and hoping you get some help soon.