Should I take my fiance back? Should I trust my head or my heart?

İts hard to say that he will not do it again ot he might do it again. Trust is really hard to break. Its all up to you now. Just do not let your decision be clouded by your emotion. Trust your instinct. At least if you would take him back, take your time before you get married with him so you'll see how long could he last. Good luck to you and hope you'll be happy.