I had a teacher who told me that she viewed it like a scale: faith on one side, doubt on the other. When faith outweighed doubt but even the littlest bit...we could move mountains. I've kinda stolen her idea for myself.
See, I'm flawed, fallen, fickle. My heart doubts what I know is true. It's why it's so important to tell others that you love them. It's not that they forgot, it's that we as humans need that reminder.
We're no different when it comes to God and His love for us. We need to ask if He'll be there because doubts creep in and corrupt what our heart knows to be true.
So ask the questions, allow the doubt to exist. Why? Because we serve a God who is big enough. He can take our questions, He never tires of reassuring the sincerely seeking heart.