yes it sounds like its self injury
it can take many forms and while cutting is the most talked about a person does not need to cut to be a self harmer
i say 'sounds like' because the motivation determines it more than the act (in the sense that S&M is not self harm but can involve similar acts to self harm) and since im not a expert i could be wrong
you should def bring it up again with your T as it can get much worse if left to one side and it is clearly something thats on your mind