I was like this the whole time I fed my son because every health professional I saw told me my latch was fine. With my second child, things looked to be going the same way - I still had sore nipples which wouldn't heal - but luckily, that time I had a HV who was alert to the issue of tongue-tie, referred me to a lactation consultant who not only dealt with the tongue-tie, but sorted out the thrush and bacterial infection going on, as well as helping with attachment. I went on to exclusively breastfeed her for 6 months, before weaning onto solids. I'm still feeding her now at 21 months. I'm not suggesting you've got the same issues as me, but it wasn't that I couldn't breastfeed, as I feared, but that I had an awful lot preventing me from feeding and none of the health professionals, whom I expected to be able to help me, could. So please take heart from the fact this is nothing to do with you, your nipples WILL heal when you get the right help.
At 6 days I'd be very surprised if you had all the problems that I got into, most likely at this stage the positioning and latch needs working on. Is there a breastfeeding support group anywhere nearby you can get to? They would be the best port of call first off as if you keep attending you can receive ongoing encouragement and support. Otherwise, a breastfeeding helpline might at least be able to offer further information and support. Best of all, if you could get it, would be a referral to a lactation consultant - it's worth asking the midwife for one, perhaps a talk with your trust's infant feeding co-ordinator (they are sometimes lactation consutants) - just don't give up until you and your baby get he help you deserve. Once the latch is sorted the nipples should start to heal quite quickly, within a couple of days.
Here's some info on how to improve your latch: kellymom.com/ages/newborn/bf-basics/latch-resources/
Right now, you can take paracetamol, 2 tablets up to 4 times a day to ease the pain before feeds, take about 30 mins before feeds. It sounds terrible but if you can bear to feed frequently then baby will be less hungry and less aggressive in feeding, and feed from your best side first so that the most damaged breast is spared the strongest sucks. In between feeds you can wear breast shells to stop your clothes.
More advice on what to do in the meantime to make life bearable:www.motherandchildhealth.com/Breastfeeding/Becky/cracked_nipples.html
If you notice pus in your nipples then they have become infected and you will need to see a doctor to get some antibiotic cream before they will heal. Likewise, if you notice white spots in your baby's mouth, or a whitish fur on his Tongue, alongside your nipple pain, then it's pokey you both have thrush and again, this will need to be dealt with before the nipples will heal. Look on the Breastfeeding Network website for their downloadable leaflet on thrush for more info on this.
Well done for persevering - you've done so well, you really deserve some help to keep going and when you get it, those nipples will heal, and you'll be on your way. Let us know how you get on.