That would be a tough situation. You said you're getting your own place in March, right (you and your BF)? Can you afford the place without you working? Does Jason take his mother's side instead of yours? You might want to have a sit down with him and tell him how you feel (I know, that's not always easy with guys). It is important to be able to communicate if you see yourself having a future with him.

Start checking out the help wanted ads, and make sure that Jason's mom sees you. Make it known that you love the volunteering, and you can see something with animals being your future. If that is true, your volunteer work will look great on a resume. Also, when his mom tells you to take a certain job, you can politely decline, say something like, "That looks interesting, but I'm not sure it's right for me. I saw a few in the help wanted ads, that look pretty good, I'll check those out first."