Pregnancy and RLS is pretty difficult and I'm glad to see that you have symptoms only every 2 - 3 weeks.
You will I'm sure have done the walking bit, trying to walk off the symptoms until you can get back to sleep.
As for natural remedies, some of us get a little temporary relief from either a hot shower or bath. I actually found that icy cold water gave me a breathing space (prior to starting medication). Fill a bucket of water with really cold water and get the feet and legs into it, splashing the cold water up as far as possible. It would take about 15 - 20 minutes to achieve some relief which would sometimes be long enough to let me get back to sleep. This is counter stimulation.
Wraps on the legs have helped some sufferers, also a TENS machine.
Heat using a hot water bottle or a heated blanket applied to the legs may help.
Mental activity may help some people as a distraction - it never helped me.
Also keep an eye on what you eat and drink, caffeine, sugar, ice cream, alcohol, nicotine have all been mentioned by some people as a trigger, but don't bother others.
Low iron can trigger symptoms so have this checked by your doctor and in particular Ferritin Serum Iron levels which is the iron stored in the brain. It should be up around 50/75, higher if you are on certain RLS medications. Doctors may consider 20 normal, but this is not so for an RLS sufferer.
We are a strange bunch, not everything helps everyone and it is very much a matter of trial and error.
If you put 'pregnant' into the search engine at the top right it will bring up a lot of posts. It is a very tedious task to wade your way through them.
Also consider any over the counter medication you are taking that could trigger symptoms, anti histamines, benedryl.
Anything mentioned above should be considered carefully as you are pregnant and if you have any doubts at all check with your doctor.
We are not medical folks, just fellow sufferers who want to help