I have been having real problems getting Sophie to latch on properly - she was 13 weeks premature and has just been breastfeeding for the past 3 weeks or so. I was using a nipple shield because she had a weak suck with being so early, but I want to get rid of that as I've heard they are only for short term use. She has been doing exactly the same as your LO lately and I was starting to think we'd never get the hang of it.
However, the past few days I've been doing quite a lot of snuggling with her and she has actually started latching on herself and when she does that she latches on perfectly! Try just spending loads of time snuggling and let your baby nuzzle around the nipple and you might just find he latches on himself. I find that if I hold Sophie against my chest, she makes her own way down and can latch on totally by herself. She kind of bobs her head around and opens her mouth really wide and just goes right on with no help from me.
I was also reading last night - I think it might have been on La leche League website - that there was this breastfeeding group where several women were having latch problems, and they were told to hold the baby between their breasts and tickle/rub their feet and every single baby latched on perfectly on their own. Might be worth a shot!