Looking after Dad.

I have tried to paint a positive picture of my move to Speyside. Of course it is beautiful, there are many ways to spend time and I have enjoyed the best winter the area has seen for 3 years. So what is the downside?
The clue is in the title.
Caring for someone reaching the end of their lives is always going to be difficult I think. I moved up here to enjoy the outdoor life but the main reason for being here is to be here for Dad.
Last winter he was on the edge of death and I was convinced with daily contact (twice daily actually, sometimes, 3 times a day) I would have a positive impact on his health and state of mind.
Perhaps at first, I did. He has multiple health problems as anyone of 82 does. He had a stroke just under 3 years ago when Mum died. He has mainly recovered from that but it did result in Parkinsons Disease. He has had Menieres Disease for many years and this causes inbalance and nausea.
Actually what is the biggest problem is his failure to eat and drink enough. This causes a UTI, then he drinks even less because he is afraid of being sick. The constant use of anti-biotics seem to be resulting in the infection just not clearing and I have to sit opposite him as he stares at me in mute appeal.
But what can I do? He needs to drink 2 litres a day. When I stand over him, (figuratively), he will get through a litre. It isn't enough.
So it's back and forth for appointments to the doctors, out-of-hours service for emergency prescriptions, in addition to the usual appointments for eyes, ears, teeth, check-ups, feet...
The worst aspect of all this is that he is depressed and angry, feeling that I'm nagging him. He doesn't seem to understand that the only person who can keep him healthy is himself.
The dear doctor is so patient with him but tells him the same thing over and over.
It does get me down. I feel selfish for beginning to resent the time, the emtional cos(t and money) I put into his care and the lack of response. Then I feel worse for feeling resentful.
So there...the downside.