Those may or may not be symptoms that you are going to be terminated.
However, if you feel uneasy about actions that are taken or not taken at work and how they affect your career, that is almost always a sign that you need to take action. You need to trust that little voice in your head that is giving you a warning.
How would it harm you to try to fix the situation even if they were not planning to fire you?
Talk to your boss privately. Express your concern that others are being assigned prohjects you had hoped to work on. Ask him what you can do to get these types of assignments. Specifically ask for work when you have none instead of relying on someone to give it to you.
If your boss is noncommital about your future assignments or is unwilling to give you a task when there are clearly some that have not been assigned, then directly ask if he thinks you have a performance problem and if so what do you need to do to fix it.
If you still feel uneasy after this conversation or if the suggestions for improvement are things that you strongly disagree with, then it might be time to start looking for a new job. If any suggestions are things you think are silly or mildly disagree with, then try them anyway. Your boss's perception of your performance is more critical to whether you are fired/promoted/stuck doing work you dislike than your perception. So if you want to stay, at least give the suggestions a fair shot.
Even if it is too late at this place to make the correction, it is important to understand the problem before going to the next place or you will just have similar problems there. Or at the very least you will find out some of the things you need to be asking about the company culture when you interview for a new job.
Learning to ask for constructive cricism, learning to hear it without getting defensive, and then acting on the criticism is a career-enhancing move. Sometimes the actions are to move to a differnt job because the differnce in expectations is just too great, but much of the time there are things that you can fix that will make this job work better for you and make your boss happier.
Worry about whether you are getting fired is almost always unproductive. Taking actions to improve your work relationships with your boss are generally helpful evn if you don't have a perceived performance problem. What boss doesn't want to have employees who care about their preformance enough to ask what can be imporved and then work to improve it?
Rememeber, it is highly unlikely you will be able to fix a problem that you don't know exists. When you are are uncertain that your work is being well received, then you need to find out what the problem is.