Pregnancy Test

40 days ago I had my usual period. I started a birth control the Sunday that followed. 10 days later I had vaginal bleeding for 5 days. I stopped the birth control and haven't had a period since.
This last Tuesday I took a pregnancy test and it said that I was not pregnant. I'm planning to take one again on Saturday, but I thought that before I do I would ask everyone's advice. What do you think might be going on? I haven't seen a doctor since the medicine went wonky, but I do have an appointment on the 8th. What do all of you think? Should I take another test or wait for my doctor's appointment?