What Does A Red Mark On Lower Abdomen During Pregnancy Indicate?

Hi, throughout my current pregnancy I ve noticed a mark on my lower abdomen. As I ve gotten further along in my pregnancy it has a reddish tent to it and its also gotten bigger. I m 25 weeks and I m really scared to mention what I m noticing to my OB because I don t want any bad news. I m not very active, I havent done anything to cause a bruise. I feel like its internal and that scares me.