Lap scars (14weeks) stretching/ tenderness?

Alyssa
Does anyone else have Lap scars? 
I had surgery in December for tube removal due to an ectopic pregnancy.
I noticed my scar felt very very tender this morning when I woke up and there is a small grape sized lump underneath one of my scars.
Should I be concerned about my expanding tummy? Is it normal for it to become tender? My tummy is growing quite quickly as this is my 4th pregnancy.
Any advice or experience would be greatly appreciated!