What Causes Missed Period And Dizziness With Urinary Incontinence?

i have missed my period this month. i get a little bit dizzy sometimes. i am on birth control. i took 3 pregnancy test and they ALL came back "not pregnant". i smoke. lately, i am "leaking" i guess you could say. my underwear seems to be wet as if urine is leaking out and i can not do menges (where you try to stop urine flow while going to the bathroom). why is this? please help