BPD 2 here,
Your age is a very important factor in diagnosing BPD. For example, teenagers are often misdiagnosed with Bipolar only to find out they were struggling singularly with depression or anxiety. It is really hard to diagnose until you have reached adulthood.
But no matter how old you should ALWAYS get a second opinion.
Another big sign is if your family has a history of mental illness. For example, my mom and grandmother were bipolar (bipolar is more common in women than men)
Also my aunt, great uncle and grandfather are all on welbutrin (mainly for anger) on my dads side.
Also family history Alcoholism and mental heath issues could have genetically influenced your (possible) illness
For me the biggest and most important indecator is if my close family and friends start noticing a problem. Bipolar makes it really hard to identify what behaviors are your 'normal' and which are not.
the close people around you should be able to easily identify what your 'normal' does and doesn't look like.
For example my dad has always been the most aware of my illness. I will be on the phone with him a country away and he can tell if something is off even if i feel totally normal.
So its REALLY important to have a close friend/family member who is aware of your situation and can identify if you are okay.
I truly hope you are able to get a medical asap & are free of illness.
I wish you the best & if you have questions or worries feel free to message me.
Can you describe your symptioms? And also: how long do these moods last?