I also did meth and the second I found out I was pregnant I stopped and I even quit smoking. I'm terrified my baby's hurt too. I found out at about 6weeks. I was not using heavily or daily but I did snort and smoke more than a few times but in small amounts.
I don't condone it but I have been using for years I stop immediately when I found out I was pregnant but I have slipped up a few times while I'm 20 weeks now and docs said bubs is healthy and all good. I may just be lucky but a few hiccups shouldn't worry u too much if you only smoked it, I shoot so it could have been fatal for my bub.
Meth during pregnancy can be very detrimental to the baby. It can cause a baby to be very small at birth or to be born very premature. It can also cause multiple various birth defects. But because of the few times you used, there is a chance that your baby will be OK. Only, of course, f you stop all drugs from now on, eat healthy, stay hydrated with non-caffeinated, non-diet drinks (no sugar substitutes except for stevia) and continue with moderate exercise. Make sure you get careful prenatal care and be honest with your doctor about your one (or two)-time use. If you don't trust your OB enough to be honest with them, find one that you do trust.
Every pregnant future mom worries about the outcome of her pregnancy, even in the best possible circumstances things can and do go wrong. But there is always hope and grace. Good luck to you.