I dnt no if i shuld worri or nt, i startd my period nd it was gd fr 2 months but i hvnt strtd for 1 yr nw?

i have startd my period nd i was doin ok for 2 months u no came on for bout 6 dys or so but after february 2007 i havnt started went to the doctors but they keep saying do a blood test so i hardly go much i went about 2 weeks ago nd had to do a blood test AGAIN so wah shall i do?