Three months is usually not enough time to determine if minoxidil is working, so I would continue for at least another three months. The effect may not be noticeable unless you have been experiencing a lot of shedding ("hair fall"), in which case a decrease in shedding is a very good sign; otherwise, you may just notice that your hair loss isn't getting any worse. If if you haven't already seen a dermatologist or a hair transplant surgeon who could properly diagnose the cause of your hair loss, I would certainly recommend that. Assuming that you are a man and have ordinary male pattern balding, or androgenetic alopecia, the most important thing is for you to get started on finasteride and possibly low level laser therapy (LLLT).