What Can I Do? Help Me PLEASEEE

I've been with my boyfriend now for five months and out of those five months his mother has been on and off mean to me. She's calling me names like priss and b**ch. And some days she can be super nice and just Saturday on my boyfriend and I's five month, while he was mowing, she flipped out at me. Calling me names, and telling me all the things wrong with me. All my flaws and anything really what her mouth could tell me.

What can I do? I am super nice to her, I have done nothing wrong to her, and she has these random hate moments to me almost every other week. To be honest I am getting really tired of it. And I already have bipolar depression, she isn't helping me at all.

Breaking up with my boyfriend is completely out of question. But really I need someones opinion on this. I've forgiven her many times and this time I am not.

What do you think I should do? Am I reacting the wrong way? Am I doing something wrong? What can I say to make her stop? What can I tell my boyfriend.

My mom doesn't want me around Coty if his mom is with him. It's breaking our relatioship apart.

Help...