Could i be pregnant? my tubes are tied!!?

my tubes were tied in 2007. my period usually comes like clockwork every 27-29 days. i am now 2 1/2 weeks late. i have been very emotional and on edge. i am so tired all the time. and i keep having these sharp pains in my pelvis (which i never experienced with my other children). but, the pains come and go, they are not constant. my are not swollen, but my are sore a lot. i have cramps that come and go, not like a normal period. but, i keep having discharge leading me to believe i am starting. but, when i go to the restroom i discover that it is only discharge. what do you think is going on?