Can you have a light period and still be pregnant? would have conceived in oct. took plan b and have had a period each month since. not feeling right.

Odd things happen: It is possible, but not that common. Plan b however has about a 10% failure rate. The rate is higher if the person taking it is large. Iif you dissolve a chemical into a larger container, the concentration of it goes down and, plan b works by being just a little bit of an overdose. oh, it also changes menstrual cycle for one and often 3 periods. including spotting.