I'm assuming this could be the effect of being low carb and getting low blood sugar as i'm not used to it, but i'll explain.
After introducing brown rice soaked ( as i believe I have problems digesting paleo amounts of fat and protein) about half an hour after eating it i feel slightly jittery and feel kinda fatigued in the joints. Other than that I think introducing rice could work
Is this a sign that I should stop or is it just because of being low carb until now? ( I probably ate 100 g of cooked rice)
Or is this just because I fasted from yesterday dinner to 5pm today?
Or maybe I need to eat more as i didnt eat before?
For dinner I had, a steak and my dads fat off his steak :P
salad, 700kj of dark chocolate, and 100g of rice
Is that 100g of raw or cooked rice? Your reaction sounds more like blood sugar than bowel (if it was the latter, you might want to look into avoiding starch a la the Specific Carb Diet). It's probably also worth trying another starch to rule out the possibility of an allergy to rice.
But it certainly sounds like what happens to VLC dieters when they take in a large amount of sugar or starch. For VLCers who want to add starch it's important to give yourself time to re-acclimate. If it were me, I'd ramp up my starches and get to the point where I'd eat 150 g of carbs/day* for 3 days. If symptoms don't improve, then I'd look into other possible issues.
If you determine that it's a temporary reaction to a VLC diet and you want to stick with the brown rice, try Stephan Guyenet's approach to soaking brown rice.
Note: this 150 g of non-fiber carbs, not 150g by weight of starch.
Generally, if a food makes me feel poor and no other symptoms or variables are present, I think it's a good idea to STOP EATING IT
To answer some of your other questions, yes, potatoes might be a good alternative. I've personally found that some of my old GI shenanigans surface (occasional gas, tummy grumbles) resurface when I eat potatoes (I eat them only two days a week), but it's never to the point of uncomfortable bloating or any major issues. If you get the same issues as I do, I'd consider peeling your potatoes before cooking them.
Do you feel good without the rice? Then you ate the rice and got symptoms of low BGL?
If so, then what's most likely happened is that by eating paleo, you have reduced your insulin resistance (we all have gotten more resistant over time by eating SAD) and we get less resistance by eating paleo, primal, or any other more natural/ancestral way of eating... If this is the case then most likely when your body released insulin in response to the rice, you got a reactive hypoglycemia.
BGL went higher than your body is used to - released insulin to drop it back down - BGL then went lower than your body is used to - left you feeling shaky and bad.
This has happened to me and my wife on occasion after eating things that would cause a rise in BGL.
Contrary to the previous posters advice, if you are vlc you are going to be insulin resistant so your body can make the most of the blood sugar I'd does get. I remember a thread over on perfect health diet saying that some people that some people found rinsed white rice OK when unrinsed was not.
Is this question based on a single meal with brown rice? I think it will be very difficult to diagnose any issues from a single observation. You might try a second time, perhaps a smaller amount. Do you fast regularly and then eat a large meal as you did in this circumstance? Various factors could be in play here.