I'm thinking the reason you're seeing the number combination more and more is because you wonder about it more and more.

The subconscious will try to help you solve the mystery by putting your conscious attention on related things so you can gather as much information about it as possible.

Fear is one of the most potent manifesting emotions we have. The more something is feared, the more it tends to manifest.

So there's a double whammy here. Both your subconscious and your fear make you see the numbers more and more.

Below is one way a person might get to the desperate point you're at (just a guess for your individual case, but one way it could happen):

You started noticing the numbers because they resonate with you. There was 11:23 on the clock and it was correlated in your mind with your birth day.

Then it happened again. And you started to wonder if there's a meaning to it. (There wasn't, not at that point, it's just that you are naturally predisposed to notice numbers that relate to your life, like your birth day.)

Now that you actually wondered if there's meaning, the subconscious kicked in, like it does when there's a mystery. You started seeing the numbers more often. And the more you saw them, the more mystery there was, which resulted in seeing the numbers even more often.

Eventually, the need to solve the mystery became such a focus that fear entered in with, "what if it's a bad omen?" type of thoughts.

Suddenly, the numbers show up even more often, and each time the fear gains strength. The point is reached where it seems real that the date represented by the numbers is the date when something bad is going to happen.

Even if the birthday is all good, something will happen to "prove" the prediction. Maybe a child skinned her knee. The child is good now, and nothing else even slightly negative happened, but that incident will be used to prove the prediction.

Living in fear is not fun.

Now that you know the reason, there is no more mystery.

You'll still 11 and 23 and 11:23 here and there. But it won't be a mystery. You notice the numbers because you have a natural affinity for them, not because there's any other meaning than that.

If you're still anxious or the fear continues, consider getting professional help. Because living in fear takes away all quality of life. And you deserve quality of life.