Custom field on user page
Take a look at the Field Group module. That will enable you to group fields under a heading as you require. You can add groups on the form or on the display independently.

After you enable the module the display editor at Administration -> Configuration -> People -> Account Settings -> Manage Display will show a new entry to "Add new group". Add a new group of type fieldset, give it a title as required and set it to be "open" (not collapsible). You can then drag and drop individual fields into the group.

By default the group will display in a box. If you don't want that, the CSS to override it is pretty simple, eg:

body.page-user fieldset {border: none;padding:0;margin:0}