Is it ok to use ice hot for lower back pain when theirs a possibility of pregnancy?

Not really: Hot tubs, electric blankets and things that increase your body temperature are not a good idea during pregnancy and are associated with a higher incidence of birth defects. Though a simple hot pack not not cause much increase in your internal temperature it is probably safer to use ice.

Talk to your OB: Icy hot should be fine, but talk to your OB and they can help provide you with options for your pain.