A true love should make every aspect of your being yearn and ache for him/her. Your heart should beat for them and your soul should reach for theirs.
If your ex was your first love, it's normal to keep a little place for him, regardless of how bad he treated you.
The first person you love is always more intense because it opened up your heart and showed you what love was like, it was something you didn't expect or know how to handle, that's why you will always remember him.
After that you went into a relationship knowing what to expect and how to handle it, it wasn't such a shock to your system, and therefor it won't have such an impact.
Your husband does sound like a good guy, most would say that's really hard to find in a man. Every time you find yourself allowing your ex to creep back into your mind, just think of what your husband does better, and what you like more about him. Eventually you'll start to naturally put your ex out of your mind.