Although the sperm friendly lube is meant to help Its definitely still possible to get pregnant without it.
Controversial but... could you put a small amount in (the pre-seed one is meant to be inserted) and pretend it's natural! Also, if you're not seeing fluid and he wants friction doesn't that make you sore?
Your DH is being a bit selfish in not wanting to use lube as it can be painful without. Can't he compromise during your non fertile periods to use lube so you can enjoy it? It doesn't matter if he doesn't finish inside then can finish off another way