Constipation Problems. Help?

So I had some constipation the last week. I went to the doctor and they said I was full of crap, so to speak, and I needed to try some Magnesium Citrate. I took half the bottle and went to the bathroom a decent amount. They also x-rayed my stomach. Now my stomach still feels hard and I dont think I've gotten everything out. I haven't used the bathroom today. What should I do?