scared of another miscarriage!

Bev
Okay so last year end of September i had a miscarriage, had a scan at 8 weeks and was told no heartbeat and baby had died a few days earlier... absolutely devastated! I have two girls already aged 5&3.
After my miscarriage i found out i had very very low Iron and Vit-D and doctors suggested that could have been the reason i miscarried- really helped to make me feel better... NOT!! so been on tablets since to boost my levels and i am now 4 weeks + 5 days pregnant and i am so scared of having another miscarriage! It was the most painful, heartbreaking thing i have ever been through, doctors seem positive that it wont happen again but I can't shift that feeling! 
Anyone been through the same with Iron levels etc? x