Pregnant On the Pill, Or Something Else?

Hi all. I take Seasonale (so I only have my period once every 3 months) and have for over two years now, and I haven't had any problems until a few days ago. I went to the bathroom yesterday and there was a chunk of dark, mucousey-looking stuff. Later that day I had some very light bleeding (a brighter color). Every time I've gone to the bathroom since there is a very faint trace of a darker discharge color, but nothing anywhere near heavy enough to even need a panty liner. I started thinking about it and the last few days I've been craving all sorts of things (mostly chocolate) and yesterday I completely gave in to all of my cravings and stuffed myself with anything I could find. I've also been more tired than normal for the last week or so, and have had very mild abdominal cramping (hardly even noticeable most of the time, though it has slowly been getting worse).

About a month or a month and a half ago, I missed a pill or two and was late (by 12 or more hours) taking a few pills (this was over the course of about 2 weeks). I was still sexually active during that time. Is it possible that I could be pregnant? Other than the symptoms I listed above I have no other symptoms -- no tender, swollen breasts, no sickness... maybe a little nipple tenderness but nothing big. I haven't had any major diet changes or changes in stress, activity level, etc.

Would it be worth it to take a pregnancy test at this point, or is it too early to tell? Also, I am still taking my birth control pills as the pack isn't done yet. Will the pills interfere with a home pregnancy test? If I'm not pregnant, then what else could be possibly causing me to have this light spotting?

Thanks in advance for any advice.