Lately I Am Having Very Sharp Pains In The Chest

Lately I am having very sharp pains in the chest area. I have always had these on and off in the past but they seem to have become more persistent. I do not believe it is my heart, I have no other symptoms. I feel fine generally. The pains are very sharp, worse on breathing in, sometimes out too, if I try to fully empty or fill my lungs. The pains are not always in the same place and seem to move about in my chest, but mostly under the ribs. I was recently woken up by one such episode. I sing in a choir and it is even preventing me from singing comfortably and is impacting on everything. What is it due to? I can't understand what this can be. Any help would be much appreciated. May be I should add that I am premenopausal. Thanks.