I am dreading my birthday.

[vanlassie]

5. Alarimer, I think you just said a mouthful.

"Thinking about it makes it seem worse."

So you are having a lot of thoughts and they are making things seem worse. Have you heard anyone say "Don't believe everything you think?"
I love that because it is so true! Just because my mind tells me a thing does not make it true.

In fact, my mind tells me bullshit false stuff all the time.

What I suggest is to empty all the current beliefs you are hearing abut your birthday on to a piece of paper.
Like this:
My life is not good.
I never should have taken a job here.
My ex is...
I will have to eat alone.

Like that.
Then, see if you can verify if those things you are believing are really, truly true. Hint: If they will happen in the future, since you are not omnipotent (I assume!) then they are unknown. Then when you get rid of the lies you have been telling yourself were true, you will have something you can make a choice about.
Making a choice about what you will do next is how you regain control and peace of mind over your life. Write down the choices you make. Keep them close by, and follow them. Maybe you want to make a choice about your birthday? What you will do? Where you will go? Choose.