Took plan b and got a week long light period 2 weeks later (a week earlier than expected period). was this a side effect or was it too long to be one?

Periods are crazy: You likely were stressed out after having unprotected sex. Stress can cause hormones to do unexpected things. Women can tell they're stressed if they are having irregular periods--especially if they are usually regular. The change in timing can also have been caused by the plan b. No worries, it'll get back on track...Just always use a condom, and you'll have less to worry about.