What Causes Missing Periods?

I'm a 21yr old. Wit weight 40kg. N height 5 feet one inch. I've regular periods. My last period was on 20th April. Aft that i had an attack of typhoid. N was hospitalized. I was positive was leptosporosis also. I was given ceftriaxone n doxycycline. I was supposed to get my period on 18th may. Still not got it. Wat shld i do to get my period?