I agree with jwaugaman. Most doctor's do not recommend intercourse until at least 6 weeks. I also think that between the plan B and the recent childbirth, it seems very normal that you would be having irregular bleeding. I have heard that many women feel sick for a couple weeks after plan B and that it can be hard on your body. If you do not want to get pregnant again soon after, you should really consider using condoms or going on actual birth control at the recommendation of your doctor so you don't have to put your body that is so fragile after childbirth through that. Just my opinion, please don't be offended. It is normal to bleed for up to 10 weeks postpartum. I wouldn't worry.
first of all.... you should not have intercourse until 8 week post delivery. Your body is completly out of wack. Having intercourse probably triggered you to start bleeding again. You should wait until your ob gives you the go ahead to continue your normal routine with your partner.
I bled on and off for almost 8 weeks after my 2nd child. It is very normal.