People think I’m exaggerating when I talk about how bad my periods are

It is incredibly frustrating having a handicap that most people don’t even see as a problem. It’s even more frustrating when that handicap is something embarrassing like my period. Even people that know of my heavy symptoms think that I just complain a lot. Even worse than having others think I’m weak is the fact that I feel weak myself. I can’t pursue my fitness goals consistently because I am practically incapable of doing ANY exercise during my period. Does anyone else feel this way or at has at some point? How can I overcome feeling like my period makes me weak?