It’s not unprotected if you’re using the pill correctly - the pill is your protection, it’s just condomless. The pill is far more effective at preventing pregnancy than emergency contraception. Plan b works by stopping ovulation, if you’re using the pill correctly you already do not ovulate so the plan b will do nothing, except potentially cause unwanted side effects, which you’re likely experiencing now. Irregular bleeding is a potential side effect of plan b but it’s also normal to experience irregular bleeding at any time on the pill.
There’s an emergency contraceptive pill called EllaOne which actually decreases the effectiveness of the pill and the pill decreases the effectiveness of it so if you had taken that you potentially actually increased your risk of pregnancy, not decreased, so it’s important to educate yourself and consult a pharmacist when taking emergency contraception.