Suggest Treatment For Pain In Rib Cage

Hi.. i am a 35 year old female. in good health and wieght. i have pain in the lower left front side of my rib cage, but feels behind ribs... it feels like a side stitch common to exercise etc... but has lasted for 3 days and appeared in my sleep and i woke up to it. It sometimes is dull pain for example when breathibng in and sometimes stabbing severe when moving or laying on it.. no shortness in breath at all and still able to exercise but have to breathe through pain or slow down. It worsens to bend over or lay on the side.. but is ok to sit most times, sometimes it hurst sitting also. It feels intense when i take a deep breathe but still like a side stitch, but not all deep breathes. the pain fluctuates. I have had a stitch before when running but it never lasted longer than the exercise period. to bend over to side or downwards makes it rush to a really intense bad pain. any suggestions? side note: i do have pectus excavatum.. and im not constipated and have passed gas.