Is this bulge normal 3 months after diep flap? (Photo)

If you are concerned about the second photo along the flank, that looks like just excess fatty tissue that may be amenable to liposuction or skin excision.  If that photo is a lateral view showing the front of the stomach, then perhaps you are just weaker on the right side.

My suspicion is that the right side where the muscle was NOT taken for the DIEP flap is actually your normal abdominal contour.  A normal abdomen is concave (sunken in) slightly above the belly button and slightly convex (curved outwards) below the belly button.  By placing mesh after removing some muscle on the left side your surgeon actually tightened this area relative to right side.  It's hard to know for sure without examining you of course but sometimes this relative "bulge" is actually a relative "tightness or flatness" of the other side.  To correct this would likely require surgery to either liposuction our some of the fat to make it look less full or reopen the incision and place mesh or sutures to tighten this side to match.  I does not appear that you have a hernia (rare after DIEP flaps).  Since some patients require fat grafting to correct slight contour issues in their breasts, your surgeon could take a bit of fat from this area.  Otherwise, insurance may not pay for correction of this abdominal contour issue as it is not considered "medically necessary".

A diep flap is a complex breast reconstruction. It is not a tummy tuck. It appears that you healed well and must be somewhat satisfied with your breast reconstruction. Typically additional stages are needed for nipple construction and shaping. Fat grafting with some liposuction can help. Your surgeon will help you.