I am a 23 year old female who has had abdominal distention for 10 months in addition to constipation. i have a pulsating mass around my belly button ?

Get checked: You could have a variety of conditions causing tis issue. I would see a doctor as soon as possible or go to the emergency room.

Need an exam: How long have you had the mass? How large is it? etc, etc. These are just a few of the questions a physician would want to ask you during a visit. Then he would examen you. It's not possible to give you a diagnosis in this limited format. Giving you a list of possible causes won't help you. You won't be able to diagnosis yourself. It's time to see a physician if your concerned