I'm building a character who is a Warlock. His patron is a great old one, which does not (initially) communicate directly. Instead, it gives the character urges and dreams, prompting him towards a certain path. It also allows the Warlock to understand some of the ancient tome the character bought, thereby giving him abilities that are associated with the Warlock class.
For the backstory I have in mind, the character would go through his initial steps as a warlock (e.g. learning some cantrips as nothing more than 'fancy party tricks') without knowing he has a contract/bond with a great old one. When the adventure starts (level 1), the character might already be aware of the fact he draws his power from his patron. This could depend on if the DM wants to incorporate it in the story or not.
Would this character have to be aware from the start he is a Warlock? That is, is a Warlock inherently aware where his power comes from? Or is it possible he believes the power comes from within, or just from studying?
If at all possible, how likely is it he would remain unaware as his powers grow, assuming he does have a base level knowledge about the magics in the world (D&D 5e), and does not have someone else telling him?