Im nearly 16, and yes its frowned upon but I'm sexually active and not frequently protected but I know the importance now and will use protection in the future, I have had my period since I was 13, and since I became sexually active I started getting my periods every 6-7 weeks, this has happened for my last two periods, and they would tend to be heavy, but 2 days ago I got my period, the normal 4 weeks after my last, and I showed signs like mood swings and cramps that day, the blood was a regular flow with a little brown, but later that day it stopped and came back the next morning lighter and a bit more brown and the same this morning, what is happening? I seem to be suffering from UTIs after sex too and I'm currently on the antibiotic clonomax.please help my mother passed 4 months ago and I can't talk about it to my dad.
One more thing, due to the length between my periods I'm worried that I might be unable to have children when I'm older and that's my dream to be a mother when I grow up since mine was so good to me, is this possible?

You should be seeing a gynecologist for answers to these questions and a thorough exam. If you don't want to become pregnant, ask the doctor for birth control. You also need to be checked for any sexually transmitted diseases.

You can get pregnant having longer cycles, it just requires more tracking and sometimes takes longer.

This could be an infection issue, or a pregnancy issue, Best wait two more weeks and try a pregnancy test.

But as all women have to get regular "female" check ups, it is time to check on infections and other general health. So you will want to schedule an apointment with your doctor