What can help conception?

Princess • I am 28. I have one baby aged 2. TTC baby number 2 and no luck :(
My hubby & I are both 28. We have a 2 year old son. I became pregnant quickly before. Now i am ttc since 6 months and no luck. I dont know what the problem is. This is making me feel depressed and worried. I used ovulation kits, pre seed & concieve plus nothing helps. I am taking folic acid and agnus cactus? Do they help conception? When should i see my dr?