I've been having the same problem for two months now. The first time it happened I saw a doctor and she said it is probably my pill. She didn't even bother giving me a pregnancy test. You should go get checked out to rule out infection as well and check for any std's. That wasn't the case for me so I was told if it continues longer then a month to go in for a pap smear (which I have yet to do) to rule out anything serious (such as cervical cancer though that is VERY unlikely). She said to take Advil or Motrin and that could help lessen the bleeding. Also MAKE SURE you are taking your pill at the SAME TIME every day. The first month it happened to me I didn't miss any and started spotting a week into my pack. It kept getting heavier and then lighter (almost like it was going away) and then heavier again but it went away with my period. The second month I did miss a pill a week into my pack and took two the next day but started spotting again a few hours later. I'm actually still spotting and due for my period tomorrow (joy). I feel your pain. Don't be afraid of sex as long as he doesn't go too deep (I've found that I'm more sensitive when I'm spotting so it's uncomfortable for me if he goes too deep, but that may be different for you) and it'd be a good idea to use condoms. If it's painful then you really need to see a doctor. I do know that stress can effect your period but, as you said, Id expect it to delay it, not make you spot.
So, go see a doctor so they can rule out other problems, and if it continues you may need to change your birth control brand. But hopefully it will go away with your period.