When do you know when...

OK, kinda sounds strange, but, I wonder when or how will I know when its time. I hate for Ruger to be in pain and last night, he was in pain. But, this morning, he was OK, not all better, but OK. I just cant handle knowing that something is eating him away and that I dont know how he feels or if he is just a little un comfortable or totally in pain. He has never been really bad about crawling in my lap when he doesnt feel good, but, last night he did.