
Aw Dannii you poor thing. I know exactly what you mean. I went through much the same thing with Imogen. The only words of advice I can offer are those which others told me and it got me through:
1. Persevere - your milk takes time to settle in knowing how much to produce for LO and how often. I can honestly say it took about 6/7 weeks before I realy felt that it all settled and that my boobs/milk finally "got it"

and were in tune with Imogen's feeding patterns.
2. Cry, rest, eat/drink when you need to - your hormones are all over the place still and doing these as and when you need will certainly help you to maintain the energy you need and to stay calm (blood sugar levels etc.)
3. Remember that breastfeeding is HARD WORK and takes time.... I felt under so much pressure (prob putting pressure o myself) to get it right and expected it all to come so naturally and be perfect at it. it did feel natural to me but it was harder than I thought, especially the first 6 weeks. Every feed is a success Dannii for you and Evie and allow yourself that success.

you are doing a grand job Honey.
4. Babies do not feed "perfectly" by that I mean they don't just latch on strightaway, suck suck suck, come off gently and then wind (oh how I wished it was like that and TBH I expected it to be like this....oooooh how naive!!) They fuss, they pull on and off the nipple roughly sometimes, they don't always latch well, they comfort suck etc. Accept this and be prepared to try different things to help LO and yourself in making feeding better for you both.
5. Leading on from above, try different things. Imogen always had a preference for my right boob. I found for a while I had to breast feed her on my left in the rugby ball position on a pillow as she seemed to prefer lying on the left side of her face to suckle (as was her position when feeding from right boob...see link below.
rugby ball position
6. LOs really do tend to take what they need so don't fret if she doesn't seem to take much. It all balances out over the day.
7. Have you tried expressing a bit of milk to relieve the pain of the build up of milk, I expect that may be what your pain is, although keep an eye on things and speak to your HV if you suspect mastitis.
8. Talk to you HV (if you feel you can) as she may be able to watch you breatsfeed and offer advice. I needed some practical help in the early stages and after a while I didn't care who looked at my baps or rearranged them to help Imogen feed!!

It really helped.
Well I may think of some more advice I can share, but there are a few suggestions that may help you and Evie.
If you are determined to breast feed I would say keep at it and get as much support from your mum etc. to help out at other times, e.g. look after Evie so you can rest between feeds etc.
but, if it is making you and Evie unhappy and you feel you would both be happier if she had formula then do it. you may find you feel guilty/sad at this prospect and I think it's very natural to feel this way. But happy mummy=happy baby andf vice versa - you have given her a really good start Dannii and be proud of that.
Good luck hun. I hope things improve for you. Keep posting for support and of course to share successes x x x