I used to have a mental block on my bhs as well. I hurt my arm doing one at my old gym (I wasn't fully ready to do the skill.) At my new gym, I took privates and they made me relearn it from the first step. The first day, they made me do some drills and some conditioning as well as practicing my bhs on one of those roll things. On the second day, they had me do the same thing then they told me I was ready to try a bhs so I tried it on a mat, starting from like a small trampoline, with a spotter. Then I practiced roundoffs on the tumble track from which I would jump back as far as I could on my back onto a mat. My coach told me I could try roundoff bhs on the tumble track onto the mat and I just did it. The first time it looked like a roundoff whip but the second time it was better. I then did it on the air track. The third private, I got it on the floor.
So basically the point is that as long as you are ready physically and that you also believe that you can do it, you can! Just make sure your coach tells you you're ready. So just practice drills and with a spotter until you feel you are ready. I hope this helped :)