If you can't spend your birthday with your girlfriend

1. Forgive me for not being with you on my birthday, and wish you a happy birthday.

2.

Sorry, I can't spend your birthday with you.

3.

I can't come to spend your birthday with you because of something unexpected in the company. Sorry, I can't spend your birthday with you.

4.

It is my greatest regret that I can't spend this birthday with you.

I'm very busy recently, but I'm sorry I can't spend my birthday with you. I will make it up to you next time.

6. I'm really sorry that I can't spend my birthday with my beloved you, dear. I'm sorry. I'll make it up to you.

Thank you, this is what I think I should say.