Can I put white flower oil for my back pain but im pregnant?

No. Although I am not an expert on chinese herbs...My friend says that the bottle of white flower oil that she has says that it is contraindicated during pregnancy.
Avoid in Pregnancy. White flower oil(bai hua yu) is a fragrant chinese herbal oil formula used for aches and pains & sore muscles. It should be avoided in pregnancy as many sources state it could be associated with toxicity, alterations in blood flow and possibly contractions. If okay with your OB you could try swimming, walking or gentle stretching, massage or yoga but let instructors/therapist know you are pregnant.
White flower oil. White flower embrocation contains eucalyptus oil, lavender oil, wintergreen oil & menthol. In general, I tend to recommend against using substances which are not required during pregnancy. I would recommend against use of this essential oil while pregnant. REF: https://www.thefusionmodel.com/white-flower-oil-benefits-uses-and-side-effects/