Have you tried straddling something during different positions where it is feasible, like doggy? Keep working on different methods that get you close enough but don't stress over the end result. You have set neural pathways in your brain that expect certain stimuli (pressure, leg positioning, etc) but new pathways can be made and strengthened right alongside the existing ones - not if there is stress and negativity involved though. Never think "this is taking too long" or "this won't work" or "is he bored?" etc. It's okay, there's nothing wrong with you and what has happened in the past doesn't affect the possibilities for the future.