That's OK Mel, you're doing great! Just keep up doing it when you can. My dad was saying last night that even a woman who has never had a child can breastfeed, it just takes persistence - actually what he said was "if you keep at it eventually you'll have a baby with a smile on its face and a woman with sore nipples" PMSL!
I never knew that! but it sounds like you're doing great so if you keep it up your supply will gradually increase.