Ok, you sound JUST like me a few years ago. I owned a mountain bike for a long time before I really started to feel comfortable. There are lots of different things you can try if you're really dedicated to sticking to it and improving, lots of good suggestions have already been posted. What really helped me get over that hump from "scared beginner rider" into "slightly adventurous intermediate rider" (haha, I'm not great but I do ride harder trails now!!!) were two things...1) being in better shape and 2) having a bike that I really like and worked well for me.

I got in better shape by road biking and commuting to work on my bike. I am on a bike almost everyday and it really helped my comfort level...even before basic skills I think you just need to feel strong on two wheels. And if you really hate riding obstacles maybe you can talk your BF into becoming more of a roadie! for a long time I thought you'd never see me on a mountain bike again

Then I bought my Santa Cruz Julianna, and having a beefier full suspension bike made a HUGE difference for me (lots of rocks and roots in the northeast!), plus it was a better fit than my old hardtail. Now I was strong and comfortable, and I've come a long way. But I think I bought that first cheap hardtail...shoot, at least 5 maybe 6 years before I started feeling great on a mountain bike! Just hang in there! I wish you luck, stay in touch and let us know how it goes!!!