about just over a month ago i got my belly pierced and it hardly hurt at all, butt now ive just found on side of the hole on top it is swelling just one side and it is really worrying me as i don't know whether it is infected or not, and whether i should go to my doctor about it?

It sounds infected.

I used seasalt and warm water to heal mine.
It healed within a week of the piercing.

Feel a cup with luke warm water, pour the seasalt in the cup, cup it on your bellybutton and lie down.

In the shower, I used anti-bacterial soap.

It it doesn't heal, you will need to take it out. It will never heal.

This is the hardest spot to have heal, for semi-regular piercing areas. I've had many friends that have had problems with their navel when they got it pierced. One thing most piercing places will tell you is to not let any clothing rub on it for extended periods, and to keep it cleaned, as fabric or a tiny piece of dirt can get in the newly pierced flesh and cause problem after problem.

So do you think I should see my doctor about it