In general women with IBD have normal periods and no particular alternative measures need to be taken. Very occasionally loops of small intestine may lie low down into the pelvis and this may make the insertion of tampons (as well as intercourse) uncomfortable, in which case it would be sensible to use a towel instead. Do whatever makes you feel most comfortable.
IBD frequently causes weight loss and this may be sufficient to lead to your periods stopping. If so you should discuss with your doctor whether your disease is adequately controlled and whether you should see a dietitian in order to increase your energy input in order to gain some weight, as long spells without periods may lead to osteoporosis.
It is extremely importatant to remember that if you are in a relationship and have had a spell of irregular or reduced periods, starting effective treatment such as diet might quite rapidly bring you back to full fertility. Therefore, it is very important under these circumstances to ensure you take precautions if you wish to avoid pregnancy.