First, congratulations on keeping your marriage together!! Bravo. What worked to keep things together? What brought your H back home? Stick with what works!!!
Your fears are a natural progression in this ordeal. They are a natural response to an emotional trauma. They are much the same as driving on a slippery road. We all know the risks, but sometimes our judgement and choices are skewed. If we are involved in an accident on the slippery road, it is a very visual and physical reminder to "NOT DO THAT AGAIN".
The same holds true in your relationship. If you can uncover the things that led you to sepration and also the things that brought you back together, you are well on your way to regaining the security you are seeking. If you have not read Michelle's books, please do so. Another suggestion is the "Keeping Love Alive" series. There is a forum foe KLA at the bottom of the Main Menu page. They are great tools to keep any relationship on track.
Your fears are exactly that..... yours. Only you can make them less intense. Your H can help, but the first step is yours. Try some simple thought stopping. Maybe if you find yourself feeling fearful, remember a favorite family event. Try singing your favorite "pick me up song". There has to be something that makes your day brighter. Use the tools around you to get you through the tough times. Focus on the good. (he's home right!!??)
Keep things simple at first, try different methods and monitor what works and what doesn't. Develop patience with your trial and error method and you WILL succeed.