The only safe antibiotic used during pregnancyand while breastfeeding is amoxicillin. I was given 875 mg once a day. Some good news is that lyme symptoms seem to subside during pregnancy and nursing. However, I was very sick during my pregnancy so not sure which one is worse, but that's just me.
I don't know about the other drugs/treatments you are taking. It is best to talk to your lyme doc and ob/gyn. I recently had a miscarriage and am also trying for baby #2. My first just turned 3 and is completely healthy and I was on amoxicillin while pregnant with her.
If you do find out you are pregnant I would stop taking everything until you talk to a Dr to make sure it is safe for the baby. There are a lot of do's and don'ts while pregnant.
Good luck.