pain in sternum

So 'm a 30 year old male and i've been having a pain in my sternum for about a month now. its gotten worse in the last two weeks or so.  I only get it in the morning as soon as i wake up. If i press down on my sternum it feels sore. the pain on the scale of 1 to 10 is about a 3. the weird thing is it goes away after i have been up for a while and doesnt bother me the rest of the day. it only bothers me as soon as i wake up when i move around in bed or when i go to sit up. I do a lot of lifting at work so i dont know if i pulled something or what but it doesnt hurt when i lift things or if i cough. it just hurts in the morning. i havent had a chance to go to the doctor because he was on vacation and now the soonest i can get in is the last week of november. so im going to go to one of those urgent care centers on saturday. I was just wondering if anyone might have an idea of what this might be? I deal with anxiety so needless to say this has been on my mind and isnt helping.