I'm in the exact same boat. Started this month and haven't had a natural, self-propelled excretion yet.
I did drink a bottle of magnesium citrate and let it do its thing at one point, and have been taking a probiotic pill every day, but so far it's just been the one magnesium citrate poop in like 2 weeks. I am still losing weight, though, so I'm not too worried. I suspect my body is just sucking up every tiny bit of nutrients it can get its hands on since it's finally able to stop freaking out from the grain intake and focus on actually nourishing itself.
Obviously I can't offer much hope for the future since I'm right where you are, but I have a feeling it will eventually resolve itself. Just keep eating pre/probiotics and maybe guzzle down some magnesium citrate if it's really becoming super uncomfortable. It basically works by pulling a ton of moisture into the bowel (it is a salt) for a flushing-out effect. Works within like 6 hours. Just make sure to drink lots of water with it.