Hi Emily,
I have had a very similar experience with anxiety and panic attacks paired or started by the physical symptoms you’re describing. I get sharp twinge like pains in my lower ribs try sternum and middle upper back sometimes. I find that when I feel the twinges I stretch my back and hear audible cracking coming from what sounds like my sternum.
I would like to bring up costochondritis which is a temporary syndrome that affects your cartilage that connects your rib to your Breast bone it can cause sharp pain in your sternum that gets worse when taking deep breaths, another reason you might be feeling pain that isn’t cardiac related would be precordial catch syndrome which is a idiopathic condition that causes sharp short lasting pain typically under your left nipple that can radiate further behind your left rib cage.
with that said anxiety puts a lot of tension on your chest and ribs whether it be by posture or hyperventilating chest tightness is common and could also cause those symptoms.
If you’re worried that it is something more serious get it checked, a trip to your GP or Local hospital could give you some peace of mind.
I made a post about my experiences that have worsened recently if you’d like to check that out too.
Good wishes
