If you had a laparoscopy and hysteroscopy, I presume your doctor did a chromotubation to see is your tubes were open during the laparoscopy and during the hysteroscopy determined that your uterus is shaped normally without any fibroids or polyps. However, you doctor may not have been able to determine that your tubes were open during laparoscopy and therefore wants you to do an HSG.
It does not necessarily mean on cycle day 21 you are going to start gonadotropins. If you are on birth control pills, your doctor may have meant other medications to start on cycle day 21 like Lupron.
I forgot to add that if you are going to do an antagonist protocol (with Cetrotide or Ganirelix) with no Lupron, they often start gonadotropin stimulation on cycle day 21 (if you on the pill for 21 days) before you even get your period.
Thank you so much for your comments. i will be going for HSG this saturday hopefully.
more over am not on birthcontrol pills. i will discuss the matter i detail with my doctor when i go share my HSG report with him. i was told to get HSG immediately after my periods and then from day 21 they can start IVF treatment. After searching from net and getting your reply i feel i need to discuss the various protocals and medicines to be used for the IVF treatment. i will go for IVF in june if required not this month.
A related discussion, 2nd Child Infertility