Hi Sujata,
How are you doing ?
I understand you concern. If you have conceived once then you will conceive for sure again.( No matter what the end result of the pregnancy was)
( Miscarriages are just like an accident, any lady can have it, but you have 97% chances of having a normal pregnancy).
Now about the medication
1.Tab.Letsi is a hormone pill which suppresses the body from producing it's own hormones, thus there is a sudden surge of follicles. So more follicles/ eggs means more chance of sperms meeting the egg.So pregnancy chances increase
2. Tab Duphastone , is Progestrone hormone which prepares the uterine inner lining for the possible baby & give a good attachment to the uterus , preventing any bleeding & early abortion
May I advise you,
Now you are blindly trying for the pregnancy, what if there is an undetected hindrance !!
Kindly see if the following checklist of investigations is done
Husband- Semen analysis at least 2- done 4 weeks apart preferably in an infertility center ( examination done by andrologist), Blood sugars
Wife - Blood Sugars, Thyroid profile
Ultrasound scans to evaluate Uterus , Ovaries & adnexa
Confirm tubal patency- most important- Tube is the connection
between uterus & ovaries( the bridge where sperm meets the egg &
forms a baby) this is size of hair follicle & cannot be seen on scans.
Being such a small opening tube can get blocked easily,
So check with HSG( Xray with dye), or SSG ( Scan with dye) or
Laparoscopy
If all this done & found normal , nothing can stop a pregnancy with God's will

Once all doubts are clear,
When you try for pregnancy, start having sex daily or on alternate days once bleeding stops till Day 10 of periods, this is not for pregnancy, it is to throw out the older sperms. Then no sex for 3 days, now young sperms accumulate. Then from Day 13 have sex daily at least once for 5 days, later is optional. So now young & healthy sperms are more . Older the sperms pregnancy chances are low & such pregnancy has abortion rates too

Hope I have clarified your query.
We can only prepare the way to pregnancy, rest is left to God, so pray well.
Do write back if any more queries
All the best
Dr.Balakrishnan