I suggest that you go to see your primary care doctor
about this problem as soon as possible. Any symptoms like this that are persistent need to be evaluated so that you can know exactly what is going on and what treatments are available to you.
I think, based on your symptoms, that the most likely possibility is that you are suffering from hemorrhoids
. These are dilated veins of the anus and rectum that usually develop later in life, both from age-related changes in the veins and also from chronic constipation. However, they can also occur in young people.
Periodically hemorrhoids will become inflamed, and this can lead to a sensation of intense itching around the anus. It is very typical for this itching to be worse when you use the bathroom.
Your primary care doctor will be able to examine your anus and help figure out whether you might be dealing with hemorrhoids. They will also be able to rule out other potential causes, such as cracks in the tissue around the anus, called anal fissures. Based on what they find, they will be able to recommend a treatment. For example, hemorrhoids usually respond really well to topical creams to reduce the inflammation and itching.