Lavender essential oil is fine while pregnant. It has a relaxing calming effect. Other oils such as clary sage oil should not be used until you are term as they may cause more intense contractions in the uterus. That being said i would only use about 4 drops of oil in a bath just incase because it can irritate your skin. Also, to be most effective be sure your essential oils are pure not mixed with any other kind and be careful as to what kind of plant the lavender oil is coming from. I cant remember the names but there are two different kinds of lavender plant one has a relaxing effect but the other is actually a stimulant.
That may be a depending on the person thing but I have never got a uti from bath oil. I have dry skin especially while pregnant and use lots of oil and other stuff in bath water. Some people may be more prone to getting uti.
No. They can irritate you and cause uti when pregnant. Maybe he doesn't like the smell and is trying to get you to stop using them.
As far as I know they are ok. At least most are but some dents have been known to start contraction. Lavender is not on the no list and I have used it with no effects. I love bath oil and salts.