Well, miss nobody, you are a somebody! I'm a tad concerned with that...Your title of name, then speaking about concern of weight, being gay and not looking to your mom for motherly advice. That's a lot of stress in itself!
Everyones body is different. 16 isn't too young to see a gyno!!!! Perhaps your system is normal, or it's stress, or being active, or maybe something is wrong! It doesn't matter whether you are gay and do not want children...The body should be respected by all cost. I am lesbian to which does not plan to become pregnant as of yet and refuse to take pills to rid of my periods because this is unnatural. Besides...Perhaps later in life you will meet a same sex partner and seek to become mother! If in the event something is malfunctioned, by all means get it checked out. It will save you worry, better health..Yet alone a better peace of mind!
P.S. If your mother does not know about your sexuality...It really isn't important. Unconditional love....Express your concern that you need to see a gyno for peace of mind.
Don't allow what may be or may not be...A curse to yourself.
It's common for girls and women to skip months between periods, but by all means...Get to know what's up from tests if this is natural for you!