Need Advice! Possibly pregnant?

I had spotting 15 days after my period that lasted about 8 or 9 days. It started out pinkish and changed to a brownish color. I have forgotten to take multiple birth control pills in the past month and haven't doubled up the next day. I have had cramping, headaches, moodiness, etc since then not daily tho. I took a test today and it came out negative but the first line was very faint. I'm wondering if I should test again in the morning or if I shouldn't bother and that its not likely that I'm pregnant. I don't want to keep taking the birth control if there is a possibility that I could be pregnant. Left a message for my doctor a few days ago but still haven't heard back. Any advice would be great.