if she tested and it all came back normal then maybe stress or somethig simple. i wouldnt worry too much coz they usually test for anything serious. if your not happy go back and ask for second opinion.
I don't believe I have I wet to the OB/GYN and she took quiet a few blood tests and she said I was normal with every single one. So she may have tested for that..
have you been checked for p,c,o,s it can cause very light periods and irregular periods.