1b1b - ds is only 4 days old - he's still learning and for a while you will need to guide him to your boob. He's smart, but not that able to help himself. What your doing sounds right. I had to shove my whole boob in both ds and dd for the first week or so until they realised that it was breastfeeding not nipple feeding.
It doesn't sound like you're engorged - just full of milk - you're obviously making enough for a big boy!
Keep feeding when he's looking for it and your boobs will adapt to his timings and they'll feel less sore.
It'll be a while before they stop feeling hard - they'll only be soft for a while after you've finished feeding then they'll be full again - magic
If you're in real agony then take a paracetamol - it's ok to take when you're feeding (not ibuprofen at this stage though or aspirin).
I got some great oil from SpiritofNature.co.uk which you massage on your breast after feeding and it just helps smooth out any lumps or potential blockages. It stimulates milk supply too and feels really soothing.
It's here
Breastfeeding oil Scroll down to Breastfeeding oil.
Didn't use it with ds and got loads of blockages and masitis once. Did use it with dd and had no problems at all.
Interestingly though I did express with ds because I thought I needed to boost my supply and ended up engorged and needing pain relief for most feeds. Didn't express with dd and had no problems. They were both the same weight at birth.
That might not be significant, but personally I would hold off on expressing at this early stage unless you've been specifically advised to by a trained breastfeeding counsellor - it could really confuse your suppply.