I am o negative blood type and had a miscarriage in august of last year due on january. they gave me the rhogam then, do i need it again if trying?

No: There is only risk of sensitization at times when there may be mixing of blood, for example during delivery or with a miscarriage/abortion. Rhogam also given during 2nd trimester in case a few of the baby's blood cells mix with mom's circulation to prevent sensitization. But if no fetus/baby or blood is present, no reason to do the rhogam. So no, you don't need it peri-conception.