I can only guess since I don't have an audio example, but it could very well be your room. To verify this, you could clap in the room that you recorded in. If you can hear distinct echoes, then it is likely your room. One solution would be to reduce the reflections by hanging up cloth and fabric in areas that are causing a lot of echoes. For this solution you'd likely be covering up corners and closing doors that lead to hallways.
An alternative (one that requires less effort) would be to choose a better recording location and better mic position. Being up close to your mic will allow you to significantly reduce how much the room reflections are captured in relation to your voice. Also, you can try putting your mic in a closet if you can. That would also cut down on echoes in your room.