Hi Mel,
I had the same problem with my DD, but times ten! When I first brought her home, I was on motilium 30mg a day, then slowly tried to wean off it, going to two tabs, to one tab a day to nothing. I also has very badly blistered and cracked nipples. As the drugs slowly lessened, my DD started crying a bit in the day, slowly increasing by the day until she was screaming for 12 hours a day.
Unfortunately, I didn't put 2 and 2 together and couldn't work out what was wrong with her until a week or so later we went to the Dr. who told me to give her formula, which I did and she finally had a happy day after about 5 miserable weeks. My supply then dropped even more and I had thrush then she got it, then I got mastitis and I was miserable!
I was tempted to give up, but thankfully (now) I didn't. I decided that I still wanted to give DD what milk I had because I really wanted to give her the best and I just couldn't seem to stop myself from feeding her no matter how miserable I was doing it. Now here we are 3 and a bit months later and I am so happy I didn't quit. We aren't fully bfing, but she has maybe 2 full bf's a day and the rest are comp. ff. Lily loves her booby and I love feeding her now that we have settled into it.
Have you read the thread about increasing your supply? It is great and helpful. Do you express at all? Maybe that will help you. I still express two or three times a day usually, I am still on motilium and I also eat oats and aktivite and if I miss any of it, it does make a difference.
I hope you can sort out your difficulties. But remember that you need to be happy too and do what's best for both of you. Good luck.