Is Hormone Injection Safe For Getting Pregnant ?

im 29 yrs old, height- 5 3, weight 72.20kgs. I got married in 2009 april, was pregnant on may 2009, had miscarriage soon and DNC later on may 30, 2009. 1 full year we planned not to hav a baby. 2010 sept, i went for a thorough check up, doctor said i hav PCO and i have poly- cysts on my right ovary . my periods is a 27 days cycle...but lasts for 2 days. doctor advised me to take METFORMIN TABLETS I.P (OBIMET- 500mg), ASPRIN DELAYED-RELEASED TABLETS USP (ECOSPRIN-75) and LETROZOLE TABLETS USP, LETOVAL®. i was under medication On 2011, april 12 was confirmed pregnant, but later it was found that its an ectopic pregnancy . so i had laparotomy operation on april 25th, 2011 and i got my right fallopian tube removed. it was 6 weeks fetus. now may 28th, 2011 i had my periods. now the doctor said if i get my next periods come on the first day of the periods and again we will go for further treatment. i am having folic acid tabs also. i am getting confused plz help at present my doc is saying for an injection which should be taken on the first day of periods till the next 5 dayz....is this hormone injection safe? if i dont concieve in next 3 months .....should i go for this treatment plz advice