i bought a car with my boyfriend but we put it under his mother's name for insurance purposes, can i take it if i wanted to?

When you say "take it" are you meaning drive it?  if that is the question, then, yes, however, if you get in an accident, your boyfriend's mom's insurance will take a hit assuming you have permission.  If you are asking if you can take it away from the mom and/or boyfriend, you will have a difficult time as there is nothing in writing saying you are the owner of the car.  You would have to take the car and prove in court that it was understood that the car was yours for all intensive purposes.  That will be had to prove.  Generally, the title will create a presumption that will be hard to overcome.  I need to know to know more facts to help.