Why does my belly split in the middle it bothers me a lot. (photos)

Although I would need a picture from the front to be sure, you likely have a separation of the muscles in the stomach.  It is called diastasis recti and produces a bulge in the midline of the upper abdomen.  The most common cause is pregnancy but can be the result of repeated heavy lifting, rapid weight gain, or genetics.  Correction is usually regarded as cosmetic and can be done using an endoscopic approach or simultaneously with an abdominoplasty. Consulting with a board certified plastic surgeon is your best bet and good luck.

Based on your pictures your abdomen looks stellar.
It would probably help if you post pictures from the front or different angles.
If you had previous pregnancies and you may have buses that ration medically called at diastases recti.
The treatment for muscle separation is a full abdominal plasty which you don't appear to need.
Best,
Mats Hagstrom, MD