Can two different breed of rabbits have babies?

I have one dutch rabbit and one big lopped rabbit I think its called, the floppy eared one anyway. The shop said they were two girls but the big one's been humping the little one. At first I thought it was just teratorial so seperated their food. We are getting a seperate hutch next week. But the little one is gathering straw and bits of fur (they've been malting cause its hot) in her mouth and put it in her bed.. Is she nesting? I hope she isn't pregnant because the 'dad' is loads bigger than her and the babies might kill her. She doesn't look like she has a bigger belly or anything though. How long are rabbit pregnancies? The big one started humping the little one like a month or two ago. Thanks! ps sorry for any misspellings I'm on my phone