Our stress levels are highest when we anticipate the worse.
If you are struggling writing suspense it is worth while checking out the horror genre. The unknown works well with supernatural elements. But the unknown doesn't have to be used on such a dramatic scale. Think about your first day at school or starting a new job.
Have you let your characters stew and worry?
Remeber it's not what your characters husband is doing it's what your lead character thinks he is doing that causes the suspense.
Is your character behaving in a realistic manner to stress. Think of the cheesy horror movies, would your character really walk into the haunted house for no reason? Or do you need to rewrite to make it more believable?
Think back to stressful periods in your life, exam results, medical tests, how did you deal with it? Did you comfort eat, cry, run or speak to others? Give your character a crutch in early chapters and then take it away.
Lastly, give your work to a beta reader - ask them to write their guesses in the margins - did they get it right?