Are you allowed to be your own lawyer?

The answer to this question depends upon the jurisdiction of the court, and what type of court it is. However, in many countries it is perfectly legal to represent yourself in court. In the UK, this is called being a "litigant in person." This is also legal in the USA. Usually, when a person chooses to represent his or herself, it is because they feel they would be better able to convince the judge of their point of view than if a lawyer spoke for them, rather than because they cannot afford a lawyer; those unable to afford a lawyer will usually be offered the option of legal aid, particularly if they are criminal defendants. 
In small claims courts, self-representation is relatively common, generally as a means of avoiding costly legal fees. However, perhaps the bigger question here is, should you be your own lawyer? It is generally advised that representing oneself in important criminal suits should be avoided at all costs, and even where a person does choose to self-litigate in a smaller case, he or she should consult a lawyer at some stage for advice. 
 
https://litigation.findlaw.com/going-to-court/should-you-represent-yourself-in-court.html

https://www.gov.uk/represent-yourself-in-court