That's normal... when you have an erection, the blood leaves the penis and that causes you to get soft. Most men take about 15 minutes or more before they can get aroused again. If you are ejaculating too quickly, then you will have to look into delaying your ejaculation.

You can sent me a private message if you want further details.

I'm the same. After I ejaculate I get soft right afterwards. It takes about 10 minutes to get hard again. i think its normal; i never remember being hard after I ejacualted before.