Talk to your tori
I've been practising traditional jiu jitsu for 3 years. I very much know the feeling! There's never going to be a point where getting dumped hard on your back doesn't hurt a bit, and you wouldn't be human if that didn't affect you.
If you're having confidence issues, and especially if you've got an underlying lack of fitness which makes this harder for you, the most obvious step is to talk to the person who's going to be throwing you. Any reasonably able practitioner should be able to slow down the throw so that you have time to prepare yourself for the breakfall, and so that the impact is not quite so serious.
Of course there are limits to this, because some throws do need a bit of momentum behind them. In your first year or so though, you shouldn't be working on that level of techniques, because you wouldn't be ready to do it safely.
Also, don't rush for gradings. I fell into that trap with karate, years ago. I ended up quitting because I was at a higher belt but I didn't have the confidence in my abilities to go with the belt, and other people expected things of me based on my belt which I couldn't deliver. Until you're confident with all your techniques, you're better sticking with the belt you're at and reinforcing it so it feels natural. It will come, but it will take time too.