I'm a 16 year old and one my first day of periods I had only one drop of blood.

I think you explained that you usually have a heavy flow on the first day of your period. This month on the first day you expected your period you only had a drop of blood.

Small amounts of blood from your vagina are called spotting. Spotting can also refer to bleeding that occurs between periods. There are many harmless reasons for spotting, but sometimes spotting is a sign of something serious that your doctor can treat.

There are some things I do not know about your situation:

1. I do not know if you have been sexually active recently. If you have been sexually active, then take a pregnancy test. It is possible to be pregnant and still have what seem to be monthly periods or spotting. If you are pregnant see a doctor right away for help and support.

2. I do not know if the light spotting happened on the day you expected your period to begin. I also do not know if your period proceeded as it normally does on the second day of your period. If your period came on the expected day, proceeded normally after the first day, and you have not been sexually active, then this spotting may have been a sign that your period was about to begin. This kind of spotting is normal and does not require you to see a doctor.

3. I do not know if you are on hormonal contraceptives or if you use another kind of birth control. Spotting often occurs during the first two or three months of using hormonal birth control medications.
   

4. I do not know how many years you have been getting your periods. Teens have hormonal fluctuations and these can cause irregular periods, especially during the first two years of their periods. These periods may come more or less often than expected and they can be heavier or lighter than expected.

5. I do not know if anything else in your life caused a change in your period. Some reasons your period might change include strenuous athletic training, weight loss or gain, unhealthy nutrition or eating disorders, drugs (including prescription, non-prescription and illegal drugs), and too much stress. Find healthy ways to manage stress and deal with stressful situations. Make sure you are getting good nutrition and that your weight is healthy. If you have an eating disorder, see your doctor. If you think medication or drug use might be causing irregular periods, call your doctor. If you frequently exercise strenuously and you miss your period for three months, see your doctor. If you are sexually active and miss your period once for any reason, take a pregnancy test right away and see your doctor right away if you are pregnant.

Your ability to recognize this change in your period is very useful. Write down notes about any changes in your menstrual cycle, including spotting. Include date(s) of spotting, color of spotting (red, pink, brown, or black), how heavy the flow was, and if you had any other vaginal discharge. Also keep track of the days each of your periods starts and stops. Two years after your first period if your periods are not regular, give your doctor the information you collected. Your doctor can use this information to evaluate you for more serious health concerns which can be treated.

I had my sex on 6 Feb and had my periods on 28 Feb to 6 March and from 28 March to 3 April. But yesterday 28 April is first day of my periods and am experiencing heavy flow is it normal. Can it lead to pregnancy.