Generally, at a 7DPO draw they want to see 10 or higher. 15 is better. During early pregnancy (like 14-17 DPO - when most people are getting first betas drawn), they want 20 or higher. Those are ideals, not mandatory minimums. A lower level does not equate perfectly with m/c but it does indicate the possibility of problems. This would be likely to be related with a short LP. I'm not sure if the docs prescribe the exact same supplemental progesterone for both. I'll refer you to your doc on what to take. My guess is you will be prescribed something during your LP any month you're TTC in order to boost your progesterone and cut your risk of early loss.
Think of this not as bad news, but as just news. Now you're aware of something that could have been causing your loss, and awareness means you can do something about it. So it's really a positive step in your TTC process. I definitely understand the bittersweet feeling you get when you find out what is really going on. It's partly a shock and a disappointment, and partly an "AH-HA!" moment. But this is a relatively easy-to-correct one, compared to the whole gamut of things that people deal with when TTC. Good luck with the next step hon.