Doggy style

My boyfriend and I have a great sex life for sure! But we need new positions. We have tried all of the basic ones but none of them work for us. I'm kinda short and chubby, he's taller and skinny. I guessing that's why none of them will work? But I don't know. We tried doggy style yesterday in 3 different places in his room and it wouldn't go in any of the times. Please help? I don't know what to try anymore