As the pregnancy advances you may get some pain on and off. Two common reasons are gastritis and gall bladder pain. Its common in pregnancy and can be managed easily. You should get an ultrasound upper abdomen done to rule out the latter. You can start taking some antacids/syrup etc for gastritis. Use it regularly for a week and note the effect. Also a bland diet is advisable.

Dear gemmaxpearce,
What you describe is mostly musculoskeletal pain due to pressure of the enlarged ( and still growing ) uterus, elevating your ribs especially the costal margin upwards and causing some kind of inflammation in the costochondral junction.
It is really painfull and annoying even with respiration.
If you can bear it putting in you mind that it's not a serious thing and that it will resolve gradually after you deliver, this will be fine.
If the pain is severe, you can start taking analgesics in the form of paracetamol 500 mg every 6-8 hours, and if not responding you may add a single dose of any NSAID, but not to be repeated on a regular basis.
Local anti inflammatory gel or cream may also help together with warm foments.
I hope these words were usefull to you and I wish you the best during your delivery.
Dr. Ahmed Bahaa.