Sounds like you need to take a break and see a doctor. A qualified physician can lay you on your back and press around on your mid-section and tell alot more than we could. You may have pulled a muscle which would possibly get better with some rest and anti-inflammatory meds or it could be something else altogether. If it has been going on for a month it probably wouldn't hurt to see your family doctor. Good luck and welcome!!!
DDD, osteoarthritis, fusion surgeries C-5/7 & L-4/5 both in 2006, torn meniscus left knee 2000 & 2002, buldging disc L-2/3