Once is a coincidence, twice may be a pattern. Birthdays and other special events can be a difficult time if you are prone to depression. Almost nothing lives up to unreasonable expectations, so for many people birthdays can be depressing… OP, look up depression. Everyone gets down from time to time, but depression is more extreme than that. If you seem to have the characteristics of depression, I urge you to get professional help. Start with your doctor if you have one. They can recommend a psychiatrist or psychologist or counselor. I know from personal experience, nothing hurts like depression and it can make you feel terrible. There are no easy solutions for clinical depression. Medication can help, but counseling helps more long term. Friends and family can help or they can be part of the problem - Not everyone is equipped to deal with depression. Most medical insurance covers mental health help.

One more comment. Adolescence is a time of transition in your life and experiences and expectations. I was a generally happy and well adjusted child but in college I first went through depression episodes, though I did not know what it was called at the time. I personally made it through that time, but it hit me again hard later in life. I got professional help then and it made a difference. I wish I had sought help when it first hit me.