I have now four outlets in my living room that have stopped working. I have checked the breakers and they have not popped. I have tried flipping the breaker anyway and still nothing. Could you let me know possible problem/solutions?

Pull one of the outlets. See if it has been wired using the "quick connect" holes in the back. These are known to develop bad connections after a period.
If the quick connect holes have been used, rewire using the screw terminals. The bad connection is likely to be in the last working outlet or the first non working outlet. The bad connection can be in the hot or the neutral wire.

I have now four outlets in my living room that have stopped working. I have checked the breakers and they have not popped. I have tried flipping the breaker anyway and still nothing. Could you let me know possible problem/solutions?

The breaker itself could be bad

Both answers are possibly correct so far. Test the hot side of the breaker to insure power is still passing through it, if you do not know how to test for power off the breaker then call an electrician