Time for you make friends, get a job, get some hobbies and otherwise find a life for yourself. That way you won't be lonely, won't miss him so much, and you two might even find your marriage is stronger. He'll be more likely to take your calls when you're always out and about doing things with friends or busy with work or hobbies, than when he knows you're sitting at home wanting to know when he'll be home.
I know lifestyle changes can be difficult, but it's going to be his lifestyle. When he finishes school he'll be working with the same types of people he's associating with now (educated professionals) so you need to be able to be comfortable with that. You will be the wife of an attorney.
Let him miss you sometimes. That's not going to happen if you're the one usually reaching out to him because you're lonely or bored, and he's busy with classes or school-related activities.
Also understand something. He never 'needed' you, and you've never 'needed' him. Both of you could live without the other, but the key is that you two CHOSE to be together. It's FAR better to be wanted, than needed, in a relationship. Take steps to ensure you both continue to want to be together (being needy and clingy doesn't usually help the situation).