well i started taking synthroid in late january and evr since then my periods have been off completely..i really dont know if its the synthroid or the plan b i took in the middle of february. but in february my period came normal,in march i only spotted for a couple of days,in april i got my period for 2 weeks straight and in may i didnt get my period and i have not gotten it for june im supposed to get it around the 17th...i took 3 pregnancy tests and they are all negative and i just really wanted an opinion as to what can be causing these delays?