What to do when boyfriend is very large...?

I have had a few previous partners before my current boyfriend. We just began having for the first time recently and it has been quite uncomfortable. His is wide (which is part of the problem), but then it is also really long. It is painful when he goes too far and finding a rhythm is difficult. My past partners have been more average and there were never any difficulties with them. We tried using lubricant but that didn't really help a whole lot and I don't think he knows what to do about the pain either. If you could hold the sarcastic responses, that would be very much appreciated. I know I'm not the only one in the world with this problem so some genuine advice would be nice. Thank you