What can cause this ? missing period?

i have almost missed 2 periods but around 2 weeks ago i took a hpt and got a very faint line but i think it was an evap line and if i was preg it wouldnt of been so light as my hormones would be strong enough to cause a strong line so whats causing this ? i have heard ovarian cysts can cause a false positive ? my tummy is swolen and i have been getting some wierd cramps this past 4 days they come every 2 hours and last about 2 mins but there painfull like a bad period ?