I’m about 3 months into my new hobby. Having a great time and making enough progress to feel satisfied. I frequently ride the same paved bike path. Little or no camber. The last couple times I was leading with my left shoulder, seriously twisted on the saddle, and felt on the verge of upd ing. A pretty unpleasant 10 miles. For the life of me I can not figure out why it was so uncomfortable considering my successful previous rides on the same trail. If anyone has any thoughts on what I might be doing wrong I’d sure appreciate the adult supervision. Either that or advice on where to buy a side saddle to accommodate my new twisted riding style.
Kris Holmes, you have any side saddles available?
So nothing else has changed? Was it windy? I often have trouble with wind.
Check your seat post. Is it straight? Maybe it got bent during a UPD.
Is your tire pressure too low? That can give a lot of autosteer.
Hmm, I don’t know if this will be too helpful, but I have a couple of ideas.
It is normal for new riders to develop a lean, and it eventually works itself out. I would guess that something has changed. Are you putting in more mileage than you have in the past? Did your seat get adjusted, and now you are reaching a bit further to the pedals?
Also, when I started I had a Schwinn with a metal saddle base. The saddle was actually angled to the left, so i stacked a couple of washers under the left side mounting bolts to level it sideways, and immediately my riding straightened out. I think that was an odd chance, but at least in my case it was easy to remedy.
It’s also not unheard of for not-so-new riders to develop one too, specially when something small changes in your setup. I started to lean when I went from 145mm to 125mm cranks on my 29er, then when I changed my saddle, then when I changed my tyre… 
Weirdly I’ve never leaned at all on my 36er. Even when I dropped a crank size, and when I put handlebars on. I even still get the lean now if I go on the 29er (I barely ever ride it anymore despite it once being my main ride for absolutely everything). I guess there’s just something about the 29er size that my body isn’t comfortable with, despite my brain thinking it’s the best size ever
EDIT:
To the OP - how to remedy the lean!
Grab on with the opposite hand you’re used to. Then start grabbing with both. This will make you ride a bit straighter and thus prevent leanage. Take as many days/weeks as you need to get comfortable with this, it’s not something that comes naturally to some.
Ride with no hands on the handle - even on fairly rough terrain. This will teach you to balance/steer with your hips/arse/legs and you’ll learn to keep your upper body straight while your lower does all the work.
Quit thinking so hard about it. Even in my worst leaning periods, I can ride perfectly straight if I’m concentrating on something else. As soon as I realise I’m not leaning, my brain goes AHHH, and I start leaning again. Try riding with a friend and spark up a conversation, or I dunno, sing to yourself. I totally don’t do that ever
Ride faster (as in, all-out sprint speed), and ride slower. Riding slower makes you balance more, riding faster makes you ride straighter, because if you don’t you’ll wobble all over the place and hit the deck.
These are techniques that work for me, your mileage may vary
Thanks for the replies on two accounts. First, the suggestions hopefully will help. Second, it is reassuring to hear that others have had similar issues and resolved them.
I was having posture problems with my 36" and it felt like exactly what you describe. I was leaning and turning my shoulders to the right. It was very hard to ride and it seemed to just develop out of nowhere. I tried turning my saddle to the right with no success. I then got a KH T-bar and it completely fixed any posture problem I had. It meant that I could hold the handle straight in front of me forcing me to keep my shoulders and hips straight. It’s also corrected my posture to the point where I can now ride without the T-bar and I still sit straight. I guess this is down to muscle memory. So I would recommend getting a T-bar if you don’t already have one.
My best guess: You have more weight on one pedal than the other. That’s a subtle subconscious correction we can make to keep going straight, but it pulls you to one side if you do it constantly. So to compensate, you’re twisting your shoulders but also leaning very slightly back, which tilts the unicycle frame by pushing your hips and the saddle the other way.
When I went through this, it seemed more productive to think about putting more weight on the foot that I felt was light. Then after I had gotten that straightened out, I went back to trying to keep more weight on the saddle and less on either pedal.
But as with everything, riding more was the main thing that cured it.