Dilemma

Right now I feel confused and I don't know what to think. I've been at my job for nearly two years and I have always loved it. It was challenging, exciting and I was learning new things all the time. Every day was different and after a day at work I went home feeling satisfied and happy that I have this job. So the fact that for the past weeks I haven't been feeling anything like that is bothering me a little, or a lot. I go to work every morning thinking ugh I have 8 more hours in here how am I going to survive?? Nothing is fun about it anymore and everything just seems so boring. The people in my team are ok, but sometimes I just feel out of place, like I don't belong in this team. I hate feeling this way, because I used to love my job and can't really understand how I ended up in this situation. Things have changed so much, and I don't even want to talk about how people act in this team. I used to be in a team with some awesome people, I still work with these people but we are not part of the same team, and that's mostly the thing that's keeping me from just plain quitting. I don't like working in such a competitive environment where people just do things to get credit for it and have their name up there, who gives a shit about the rest? I used to be in a team where we all worked together, worked hard to make sure we excelled at our job and had fun doing it. Now it doesn't matter if you do a crappy job, its more important if you finish 5 shitty tasks than finish 3 good quality tasks, because the person that does the 5 tasks is going to be patted on the back and everyone else is going to be told see that's how we need to be? And when I hear something like that I'm thinking excuse me?? You mean that we'd rather finish a million shitty tasks than actually concentrating on doing things right? Because I can do that very easily but what the heck? Sometimes I can't even believe that this is the same company that I joined nearly two years ago. Yesterday I was so fed up with everything that I updated my résumé and was looking at job vacancies. Today I was thinking, why was I even thinking about that? My problem is that I keep thinking that things may change again and one minute I want to run away from that place and the next I think it's not really that bad if you learn to deal with it. But how do you know when it's time to move on? Is it normal to have doubts about your job? If you feel that nobody appreciates anything you do anymore, is that a good enough reason to start looking elsewhere? If it is then why am I not certain that it's time to find something new, somewhere when I can be happy with my job again and don't have any doubts about it? Should you try to voice concerns such as these to your manager, or is it best not to? It's so frustrating having all these questions and nobody to answer them, or at least someone to help you to come to a conclusion. My head feels like it's going to blow up with all these thoughts. Partly because I don't think I want to accept it either.