Trying Not To Sleep On The Job!

I was so bored at work today, despite managing to keep myself busy until midday (which is a miracle in itself). I almost nodded off in the hours before my 15:00 lunch break! While I was on my lunch my manager decided that he was too ill to stay and went home early! He is also off tomorrow because he is meant to be on a course, though he has hinted that he will be off sick for that too!
He is due to be off for 2 days next week too and a girl from head office phoned today and mentioned that the area manager said that I would cover for those two days. She made it clear that I was the only option for covering his break. I stated, categorically, that I wouldn't do it as it was the middle two days of my 4 days off and, as I had not gained anything from the last time I covered (in fact I was worse off each day than I would have normally have been!), I really had no reason to do it. I hope that it causes the various managers to realise how valuable I am, though I very much doubt it. I would like a pay rise, as I cannot see a new job materialising in the immediate future for me, so I need something to keep my interest and professionalism at acceptable levels. Though, after my manager mentioned today that one of the many managers has stated that we have to justify everything that we do now, and that they may be thinking about cutting down the guard force again by another guard, I can't see a pay rise happening soon!
All I want is a job that pays enough to survive, and gives me something to do ALL day, and, preferably, gives me the feeling of achieving something tangible and worthwhile. Why is that so difficult to find?