Hi Fatima! I had a 3rd degree tear as well after DS almost three years ago. As long as you are religious about taking the fibre sachets, making sure that there is no chance that you can get constipated, then number 2s are nothing to worry about as it'll all come out liquid anyway. Are you taking iron tablets? If so, one of the side effectc can be constipation - however, that will be counter-acted by the fibre sachets. Do not lower your iron dosage (as I was advised by health visitor), because then you might end up aneamic and totally devoid of energy. Actually, is there are chance you might be aneamic - your description of being hit by a bus sounds like that total exhaustion feeling that comes with lack of iron.
I wouldn't advise any witch hazel etc in the bath as that can sting, and it's completely unnecessary pain after what you've been through, because down there everything heals super fast because of the high level of circulation.
It's important to take it very very easy so as not to put pressure on your stitches (by walking around, lifting, bending over etc), and that should include lying around on the sofa in a position that's comfortable (not rushing around doing anything household related, etc - that should be done by other people). That way you give yourself the best chance of recovery. Don't forget what a massive trauma your body has just been through!
I was mobile from the day after birth, but refused to sit on chairs for about 10 days. I kept myself 'runny' (using the fibre sachets) for about 10 days or so (ask your midwife for more if you run out) and then I wasn't worried about anymore and had also much more feeling/sensation down there.
With me everything improved on a daily basis, so each day was easier than the one before. I was, however, extremely 'lazy' and got everyone else to do everything other than feeding the baby, meaning that my body could use all energy for healing. If you feel that things are not improving then tell your health visitor.
Well done on delivering your baby, it's a massive feat and please allow yourself some time to recover from the experience. Listen to your body and take it as easy as you possibly can as that will shorten your overall recovery. I'm a big fan of painkillers so take what you can - simply alternatinv ibuprofen and paracetamol can take the edge off, and you can do that for quite a few days and without prescription to get you over the worst.
Congratulations on your baby - they are simply great!