[ForgetMeNot9]

Hi there Jayde! First off, I see that you're new here so Welcome!
Now, no one except for a health professional such as a doctor or therapist could diagnose you with a 'mental issue'. Not even social services. Technically, you don't have anything unless you were assessed by a doctor and diagnosed with something. However, your social worker may have said this due to whatever behaviour she/he was seeing?

With that said, some things that what would be considered as 'mental issues' are:
-Depression
-Anxiety Disorders
-Eating Disorders
-OCD (obsessive compulsive disorder)
-Personality Disorders etc.

There are many other ones that you could easily search for online if you wanted to know more about them.