There is no easy answer to this question. You can't fill in a questionnaire or do a test that will give you a definite answer. You might be bisexual if you recognise that you have feelings of attraction for women and men at the same time, but this does not necessarily have to be at the same time or intensity. What is important is that you don't deny your feelings and that you take time, at your own pace, to explore your sexuality and what being bisexual might mean to you.
It is also important to remember that you are definitely not alone, and you don't have to deal with your questions or problems alone. Try talking to one of the confidential services listed below if you are feeling concerned. And if someone tells you that bisexuals are really confused, or that bisexuals do not exist, or that they can't help you, look for someone else to talk to who does understand and care.