Don't let him call you crazy.
In my experience, I've found that guys LOVE to call girls crazy. Sure, we've all heard stories of truly bonkers things girls have done in relationships (and after them), but guys seem to label girls crazy for minor things too, or call a girl crazy for displaying any negative emotion when he doesn't think she has a "right" to feel that way.
Make no mistake, it's okay to get upset. It's okay to get angry. It's even okay to feel jealous. As long as those emotions don't lead to any violent or abusive actions, of course; it's important to know how to manage those emotions, and to say something when something first bothers you. It's tempting to say that something's okay when it's not, to keep the peace and seem easy-going. With all the relationship advice thrown at us by women's magazines and websites, it seems like the ideal girlfriend is someone who doesn't get annoyed at "guy behaviors," and someone who is passive and calm all the time. But it's healthy to tell your guy when something bothers you, rather than when you're fed up.
However, even when we do this, even when we do make an effort to manage our emotions and express them in a healthy way, things do occasionally bubble over. It's hard to handle frustration when you're already in a weakened state - tired, hungry, stressed out, PMSing, etc. When this happens, a good boyfriend will take the time to try to identify what's actually making you upset. A jerk will jump to conclusions, or worse, call you "crazy."
Don't take that shit.
You are not crazy. Say it with me - "I am not crazy." Now say it to him. You may be upset, you may be pissed off, you may be frustrated, you may be jealous, you may be a mixture of those very real and often very understandable emotions, but you are NOT crazy. Calling you crazy is dismissive, invalidating how you feel rather than trying to address the real problem that's upsetting you.
Now, if you start dating a guy and he says all his exes are crazy, beware. It's possible he's one of those jerks who's quick to call a girl crazy, and it's also possible that they were all "crazy" for the same reason - in other words, he kept pulling some dick move that upset a lot of girls. It's also possible that he's afraid they'll tell you something about him, something you don't want to know, and he thinks if he can convince you that they're not right in the head, you won't listen to them.