I am not an expert and I'm sure others won't agree with everything here, but here is my experience:
My little guy also had a latching problem. My family practice doc is also a lactation consultant (a specialist in our state) so, here are the suggestions she gave me.
First, I started using nipple shields so that I could tolerate the pain a bit more. These also got him used to a large object in his mouth. She suggested I pump and have dh give him a bottle to get him used to a longer nipple in the back of his mouth. I didn't end up doing this because the nipple shields seemed to do the same thing...however, I have so much milk that I've had to pump just to give my poor breasts a break--they seem full all the time. The nipple shields I used (Avent) were from when I nursed my dd and were apparently quite thick (according to the doc) and she did warn me that they could cause my milk supply to diminish because the stimulation wasn't enough. However, once I got my nipples so that they weren't excrutiatingly sore, I was able to discontinue using the shields in about a week.
She also had me start using a little bacitracin (sp) so my nipples wouldn't become infected. I was quite skeptical about using an antibiotic cream, but this helped sooo much, the lanolin just didn't help at all. Plus the lanolin stuck to my breast pads causing more complications.
I do pump a couple times a day and feed every two to three hours. He is 2 1/2 weeks now--over 10.5 pounds!
Another lactation consultant suggested that instead of unlatching and relatching (which was causing tons of pain) to "stuff" the extra breast tissue into his mouth that he didn't get when he first latched...this did work a little bit, too. (not ideal, by any means)
It is possible that pumping, if nipple stimulation isn't sufficient, could make your supply diminish too...oh, the crazy complications of breastfeeding!
This is my third baby and had I not successfully breastfeed my other two, I probably would have given up after the first week. I'm really glad I stuck it out, but wow--it was very painful and discouraging for these first two weeks.
Hugs to you...hang in there. Your baby will get the hang of it...