My dear, this is quite normal at your age. Your body is producing new hormones that causes changes, the feeling to have a boyfriend is one of the emotional changes that you are experiencing as a result of puberty. Other girls of your age may be experiencing these feelings too, or some others may not be. It is completely normal and boys go through similar feelings. But, having these feelings does not mean that you must have a boyfriend. Having a boyfriend can be an enjoyable experience for a young lady, but it can also bring some complications and decisions to be considered such as how you might balance spending your time with him against the requirements of your school work or hobbies, and the desire of spending time with your friends and family.
The issue of whether to enage in physical activity or sexual intercourse may also arise if you were to have a boyfriend. The most important advice I can give on that subject would be to ensure you are kept well informed about what any unwanted implications might be of undertaking this acitvity, such as pregnancy or contractimg STD's, and to ensure that you are completely comfortable with any decisions that are made instead of feeling like you must act in a certain way because of pressure.