I did sexual act dec 28 i think i'm pregnant and i have an irregular period. if i take a pregnancy test january 24th will i get accurate results?

Yes: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal period, then she is most likely not pregnant.