I have carried Shield and Full Size M&P’s AIWB for almost four years now. I very much dislike carrying in any other position. I now find 4 o’clock behind my hip awkward and uncomfortable if forced to carry there.
First, it is going to feel different than other carry locations. There is a problem when it is uncomfortable, but it should not be uncomfortable when done correctly. However, you have not said what holster you have. That makes a big difference. Leather, Kydex, hybrid? What kind of belt and attachment?
Without you having defined what your discomfort is, some general AIWB advice includes (Kydex holster mostly):
Make sure the holster has no sharp edges. Cheaper ones do, especially down at the barrel end. Sand with 200 grit paper if needed.
Good stiff belt to support the holster. I like the infinitely adjustable Velcro-closed “rigger” belts, as precise, correct tension contributes to comfort. Even adjusting the belt by 1/4” during the day, loosening or tightening, can make a noticeable difference in comfort.
Make sure the holster attachment fits the belt (1.5”-1.5”).
1:30 position so the barrel of the gun is just to the left of your right hip. Farther right and it rides on the hip. Much farther left and it may contact your pubic bone. However, there is at least 1-2” of soft flesh between that front point of the hip and the pubic bone. You can make small adjustments of 1/2” repositioning on the belt for comfort during a day while you are adjusting to the feel of AIWB.
Add the loop side of adhesive Velcro to the back of the holster, especially down at the barrel end. This will soften the feel of the Kydex against you.
Taking it a step further, buy a closed cell foam wedge with a Velcro hook adhesive piece. Place it toward the bottom of the holster on the loop Velcro with the wide part of the wedge downward. This provides more comfort while also tipping the grip in toward your body, increasing concealment. Since this also tips the bottom of the holster away from your body, it is a little more assurance that when you slowly and carefully holster the gun, along with a slight forward push of your hips, the barrel will never be pointing toward your body.
I like to have a full sweat guard that protects me from any part of the slide that may be uncomfortable.
Make the commitment to keep trying. It is worth it.