2 periods in a month?

My period before would always come on the 3rd day of the month then moved to the 6th then after i had a unprotected sex on the april 30th and took the plan b my period came on the 8th of May. then unexpectedly without any signs that i would have my period again rather than me not feeling hungry, i had my period again on the 22nd of May

And now im showing signs that my period would come

Is it normal to have 2 mensuration periods in a month?

I don't want to think that i am pregnant or what cause i didnt missed my period and if we would do a unprotected sex i would take a 1pill or the plan b