Could I be pregnant?

I've had some irregularities in my cycle before but my period is now three days late, I had some abnormal spotting and stretchy slippery mucus about a week and a half before my period was due, no spotting for a while and on day two of my missed period spotting again. I've felt very nauseous in the evening and a lot more tired than normal but other than that no pregnancy symptoms. I take my birth control every morning, not at the exact same time, but whenever I've missed I take it in the evening or double up the next day and that's only happened a couple of times and in addition to that we have been using the withdrawl method as well. I think it might be too early to take a test or worry myself but does it seem like I could be pregnant?