Ive carried a full sized handgun IWB on a daily basis for about 45 years now. Fat, skinny and everything in between.
Ive always found IWB to be comfortable and easily done. As has been mentioned, a proper holster and belt and your normal sized clothes for your size, and once you find your "sweet spot", your good.
Dont expect instant gratification though, as its likely going to take you a bit of experimenting with holsters and location, and give your body time to get used to the gun being there.
Once you do that, things will fall into place, and I doubt youll go back to OWB carry.
These days, I really like AIWB, and wish Id switched years ago. Just as, if not more comfortable, hides the gun better, protects it better, and its a good bit quicker to get it out and going.