Kathy, I think

it takes a year or so to heal from the breakup
it takes a year or so to heal from the breakup of a long-term relationship. That doesn't mean you can't date, it just means that you may not want to get serious with someone. Time spent working on yourself, learning what you really want from a relationship, taking a look at the negative patterns you may have, and gaining self-esteem will help you overcome your feeling that you can't trust a man.
The more confident you become, the more willing you'll be to set boundaries and expectations that will help you trust again. When you know where you're going and what kind of relationship you want, you'll be more willing to leave a relationship if your intuition tells you the man you're dating can't be trusted. However, the biggest thing to remember about trust is that you either decide to try it or you don't -- it's very difficult to learn to trust again without jumping in and doing it.