Donnatella, I had SPD with my first and have researched all this very very thoroughly. Basically, no medical professional will be able to promise you "no SPD next time".
What you can do is take some positive steps ie. some, any or all of the following:
go to see an osteopath who specialises in SPD who can examine you carefully and advise on the strength of your pelvis
do pilates, preferably one-to-one, to strengthen the muscles in that area
get in touch with an obstetric physio who can advise on exercises and agree to support you during your pregnancy
get in place your support network of friends/ family, or even save up for paid help during your pregnancy
leave the pregnancy for at least two years, or more- like you say, until DD is at school for example
vow to address the SPD earlier this time eg. support belt from the start, physio exercises from the start, taking it easy with carrying/ pushing/ hiking from the start.
In short maybe none of these will work but, according to my osteo and my physio, they have both worked with women who have done these things and their SPD has not been so bad second time around but no guarantees. 
Do you think that having a one year old is early to be worrying about this? It is all very raw. I am waiting a little as DD is nearly three and I still carry her around a lot and push her in a pushchair.
It is such a difficult one.
LilRedWG I feel for you hugely 