Hello. I Have Small Pea Sized Lumps In My Abdomen

Hello. I have small pea sized lumps in my abdomen below my belly button. The lumps run across my mid abdomen. The area feels tender when pressed and I have abdominal pain in that area. I feel bloated and I feel like I have gas but nothing really comes out, like its trapped or something. I have had stomach pain for years but no one has diagnosed me with anything other than GERD. Is this something common? What kind of tests may be involved?