My temper keeps getting worst I blow up at everyone from people knocking on my door to people calling me. How do I fix this.

You have recognized the problem, you just need to fix it. Count to ten or get out of the situation. Those are the easy ways. You might want to find an anger management class somewhere. That could help.

Look around at your life and see what makes you so short tempered. Don't be too proud, or ashamed to get some qualified help to guide you to getting to the bottom of this anger thing.

A few people have actual bio-chemical problems - too much adrenaline, testosterone, not enough dopamine, a hidden seizure disorder, etc.
Many people have psychological problems that are a result of lousy childhoods, beatings, angry parents, bad diet, drugs, wrong medications, all sorts of reasons.
Let's assume that you are in the second group, because you can't afford to be tested for the first group.
What would you say contributes to it?