kinda freaking out !!

i’ve been on birth control for five months now . i took a plan b on the 28th of november while taking my birth control and it messed up my cycle bad . i’m 18 days late . i took a test on january 6th and it was clearly negative . ever since i took that plan b , i’ve continued taken my birth control everyday at the exact same time ( 9 pm ) like i’ve been doing ever since i started it . after taking the plan b , i’ve had unprotected sex three times . on january 5th i started having moderate cramps . they were bad enough to wake me up . i had them all day the 5th , 6th , and 7th , but there are none today . i’ve felt like my lower stomach is full like period blood needs to come out of me but it won’t . was i protected by my birth control after taking the plan b ?? ( i didn’t have unprotected sex until almost a month after taking the plan b ) . is this still the plan b messing up my cycle ?? if my period doesn’t start in a week , i’m going to the gyno .