I get angry in such small things, but why? is there a reason because it has been weeks and it wasn't like this before?

See Below: What changed? Find out what triggers your anger. Are there any situations that increase your anger? Stress management, relaxation, self-care will help you with managing your environment better and will help you decrease some of the anger. Find a therapist who specializes in anger management to help you guide through the process.

Many possibilities: If it's clearly a change, there are many possible causes. Medical ones include alcohol or drug effect, physical illness like bladder infection, blood sugar changes, head injury/concussion, etc. Emotional ones include depression, bipolar disorder, etc. You could also be troubled by an irritating personal relationship or other stress and not realize it. A mental health evaluation may help.