Answer:
I believe that once you know your partner and that you've recognized his loyalty and his honesty to your relationship, you CAN trust him. When you get second thoughts about the relationship, you just end up screwing it up most of the time, because your partner feels that he is not trusted ... If your partner shows you he isn't going anywhere, and that he truly loves you, why would you not believe in him? However, I think it's crucial to take your time before getting into a relationship. The quicker you get into one, the more you miss important parts about the person and his loyalty to you. Take your time, and the trust will come.