Many clients ask me when they first start; how long therapy will take. Unfortunately there is no clear answer to that. 
I like the idea of Milton Erickson that “therapy is often a matter of tipping the first domino.” Sometimes an individual does not really know what their main challenge is and often the "presenting problem" is not the deeper problem that they have. So unpicking may take time. Therapy can last anywhere from one session to several months or even years. It all depends on what you want and need. The most important thing is that you get the support you need and you start to feel better in yourself (or/and the relationship)