This might sound a bit strange im 34 weeks pregnant and last few days ive been thinking/craving about biting the bathroom sponge. should i be worried?

Get a blood check: You will need to have your blood checked. It may be that you are suffering from PICA, which is usually a low blood count, specifically from a low hemoglobin. It is common.

Cravings: Cravings can occur from a need for specific nutrients.Example:people with iron deficiency may crave non-foods, like dirt or ice. Some believe a diet low in phytonutrients from green leafy veggies leads to cravings that are not satisfied from a Western diet,leading to overeating.What's in the sponge? I don't know, but don't eat it -- tell your obstetrician. He/she might want to check a blood test.

Pica: You might be anemic because sometimes those strange urges are a sign that your iron is a little low. Talk with your obgyn to check.