hi - sorry to hear about your MC, it's awful trying again after one, isn't it. 
I think the CBFM does work for lots of ladies, yes. The fact that it gave you peak days earlier than expected and that your AF arrived earlier than expected as well seems to add up to me. Normally you would have a luteal phase (the time after ovulation) that stays around the same length, 10-16 days. But the time before ovulation can vary, and that's normally what causes the variation in cycles. So if you ovulate early you could expect your period should be early too. Likewise, if your ovulation is delayed for some reason, then your period would normally be late too.
Most of the problems that I've heard with CBFM is that in the first few cycles it can give you days and days of 'highs' without giving a peak (with lots and lots of sticks needed), but usually once you have used it for a few months it 'learns' what is usual for you and everything settles down.
The other thing is that it's really like any OPK, it will normally pick up on a LH surge (which triggers ovulation), but there's no guarantee when you will actually hatch your egg post surge. It will always give you a peak when it first registers the surge, then one more day of peak and one day of high automatically.
I think it's a useful tool to use alongside being aware of your own fertility signs - eggwhite mucous, etc - and maybe temping, so that you have something to fall back on if you start doubting your own interpretation or temps. Used over several cycles (or hopefully, just 1!) you should get a better idea of whether you tend to ovulate early and have a long luteal phase or whether it changes each month for you, which might help to feel more confident that you're having sex around the right times for your cycle. Plus it does all the interpretation for you, which can be tricky for normal OPK test sticks.
It's really unlikely that stressing about getting pregnant is stopping you - assuming you started ttc again around December it's only just been 5 months which isn't that long, and I think the stress to stop ovulation would have to be extreme. That 'just relax and it'll happen' thing is infuriating - I just wouldn't jump to the conclusion that there's a problem yet. Give the CBFM another try maybe and trust its peaks...maybe you DO ovulate early?