Hi Indigobarbie
(remember you from several threads over summer) 
I'm sorry to hear your SPD has continued to do you so much trouble.
You will wear normal trousers and jeans again.
I had similar issues to you (pelvic issues causing pain, c section and large tummy due to diastisis recti - meh).
I did eventually with excellent private physio resolve my pelvic issues, pain and instability of the SI joints. And after that I managed to find enough spare strength to go on a diet and knuckle down to some exercise.
The main issue is getting your SPD dealt with. I saw on a tread the other night that you've had NHS physio but hasn't helped. Can you afford to go private? If you can do and do it now. You'll start to feel better very quickly (3 or 4 appointments). And do find a womans health specialist physio.
I found that I did not have the spare strength to diet or exercise properly until I had dealt with the pain in my pelvis. It takes everything just to get thru each day (and night!) dealing with it and obviously looking after your family.
I did wear normal trousers and jean infact my pre-preg stuff within a couple of months.
I have now really gone and done it and am currently 18 weeks pregnant so waistline looking somewhat erm pregnant.
However just after I got pregnant again my physio assured me that I would be fine and not suffer during the pregnancy if I kept up my exercises. And so far I have and have had no pain despite pregnancy and lugging around DD (18months and heavy).
You're not moaning! You're stuck in a bad place where because of your SPD, you're unable to do the sort of diet and exercise most women can undertake/start once they're 3/4months after birth. And its getting you down.
I felt like I couldn't move on when it was all still painful in the pelvic region. And it did get me down an awful lot.
I know you're after wearing jeans and trousers but how about some tunics and leggings? That helped me look stylish (as stylish as I ever get anyway) and very comfy.
I know you're posting for style advice and I realise that tunics and leggings probably isn't what you want to hear.
In terms of jeans, there are some, dare I say it, maternity ones which are "under bump" and are more than stylish enough for after. I wore my Seraphine skinny ones for ages after and I have some really fab Paige Westbourne under bump jeans which don't look maternity and are super flattering and naturally I'm glad to have them now I am pregnant again.
Look after yourself
x