I can imagine you have been thinking about it for quite some time: these strange feelings; these desires; the way your glance seems to go in the wrong direction; the lack of anything but feigned interest in the captain of the local football team. You probably imagine that there is either something wrong with you, or that the whole thing is a phase which, like acne or puberty, will pass you by quickly and without leaving any marks. You enjoy looking at women and your thoughts turn to a female partner quicker in those more intimate moments than to a male one.
First of all let us get one thing straight: there is nothing wrong with you. Everyone, whether they wish to admit it or not, has thoughts and feelings, even the most intimate ones, revolving around members of their own sex. No one else can see these emotions: there is no change in the way you walk or your appearance; it is not going to appear on a billboard beside the road where everyone can see; it is not a massive problem. At least, it is not going to be a problem if you have the self-confidence to accept yourself for what you are, a normal, developing person just like everyone else. How you deal with this development, this coming of age, depends entirely on you.
One thing that you can do is suppress your impulses. In other words, you can lie to yourself and imagine that your desires are going to vanish one day: you will wake up in the morning and have exactly the same longings as everyone else around you; the captain of the football team will be your one and only; the cheerleaders will just be a pretty clique obscuring your view of the team. You can live a lie for the rest of your days and still have a relatively normal life.
Or you can accept that you may either be Bisexual or a Lesbian, a state of affairs which I can promise you from personal experience, is not quite as bad as it sounds. You can accept that you are part of a group of wonderful human beings, probably a bigger portion of society than you imagine, and live your life to the full. In the end it makes little or no difference what you decide, you will continue to develop as nature had intended; how you deal with your sexuality is another matter entirely.
The first thing you need to do is take a look in the mirror. Take a close look at your features, at your face and hair. Has anything changed? I doubt it: you will see exactly the same person standing there as you see every morning when you wash or do your teeth; the same person who appears beside you in shop windows as your walk through town; the same person everyone else sees in your daily life. Stand in front of a full-length mirror, preferably in the nude, and what do you see? The same body that you have been accustomed to seeing each and everyday as you dress; the same person who showers, walks, lives and breaths your life, twenty-four hours a day.
The only changes are ones that you, personally, can feel: changes in your mind; changes in your emotions; changes in your perceived needs. This is where the problem lies: this is the area you need to work on in order to gain acceptance from yourself, for yourself.
There are many ways to gain acceptance of yourself from and for yourself: one is to see your reflection and accept that it has not changed, but that you have matured; one is to find someone you can talk to; one is to seek therapy from a professional. My personal preference is for the first option, each and every time, depending on how much self-confidence you can muster and how open you are with yourself.
Let us take a look at the other options too, just to get them out of the way. Firstly, who can you talk to? I would imagine that, if you are the same age as I am, you probably do not know too many people of your own age group who are capable of talking about their emotions in a deep and meaningful way; that most would be mentally over-stretched or out of their league and, depending on how much information you are willing to impart, would either avoid you in the future, or spread the news faster than a forest fire in August. Older women? A good possibility, and probably the best to hold in reserve for later; a woman who has more life experience. The drawback is, at this stage, she needs to be on the same wavelength as you are and that, depending on her age, could be a problem. Then we have therapy; talking to a professional who is so distant from the subject it is unbelievable. Sigmund Freud may well have had his theories, but we are talking about your life here and not some generalised set of psychological assumptions. And who is going to pay for the sessions without knowing the reason?
That does not mean you should wipe therapy from your list of Things To Do, merely upgrade it to LGBT Counselling where the real expertise lies. Therapy is not the answer, counselling from experts could be, but not necessarily at this moment in time.
My preference, in the first instance, is for you to take advantage of the inherent understanding of yourself which is already within you. No one can read your mind; no one can understand your inner emotions better than you can. Your mind is a wonder of nature and works faster than you can explain the problem to another person; it is adaptable and filled with information you may think you have long forgotten. You do not need to worry about Coming Out to all and sundry, that may well come later and then only in bits and pieces, acceptable and easy to handle. You need first of all to accept yourself for what you are and, if you are either Bisexual or a Lesbian, so be it. You are still a normal person. You are still You.