I'm sure you know this by now, trust is one of the main factors in any kind of relationship, so it must be nurtured at all times. Firstly, make sure that your BF has no reason to be suspicious – that means, be honest at all times. If you and your ex are still friends, make sure that your BF knows about any contact you have with him. However, it would be in your best interest to be in touch with your ex less. Remember he's your ex-boyfriend for a reason. You know that your guy loves you, so make sure he knows you love him too!