Hi , How are you doing ?
Folinext is 
Folic acid a vitamin B. You usually get this vitamin from food. But it is prescribed for pregnant women & those trying for it. It has no side effect. But by just having this tab you will not get pregnant. Keep having this medicine as you never know when you get pregnant & take it till 3rd month of 
pregnancy.
Everyone is investigated for 
infertility only after 1 yr of unprotected sex.
But if you are anxious , you can have the  following tests
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.
           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
Hope I have cleared your query
All the best
Dr.Balakrishnan