You may not have been taking the active pills long enough for you to have a "withdrawal bleed". Also your natural cycle could be all screwed up from taking the pills wrong. I wouldn't worry.
Options:
1. Wait and see if you get a period next month (end of may).
2. Take another pregnancy test in a week.
3. Go to your MD and get a blood pregnancy test, while you are there ask the MD about Nuvaring and the ortho evra patch if you still want to use hormonal birth control. For some people, it isn't convienient to take the pill every day. And the patch or ring gives you alternate options for those who miss pills often.
PS. Use backup contraception, until you have been on a hormonal method for at least 7 pills taken perfectly, 7 days into the ring, or putting on your 2nd patch.