After the 1st & 2nd session of my LHR I could see change, but after my 3rd session I think everything is back again?

I have done LHR on my full leg, under arms and bikini. after first and second session i was super happy with the result. hair was significantly less and it was much thinner. after my 3rd session ( 5 days past) I feel everything is back to normal. hair thickness and the amount of hair. Is there any reason for this? should i continue ? does birth control pill affect this treatment?