Thank you for contacting JustAnswer.
I am sorry to hear that you are having such a difficult situation with your fiance. Given that the two of you have made the decision to get married, it sounds as if it is time to have a serious conversation about your financial situation. Not paying bills in a timely way can cause serious problems for your credit and your ability to do things such as purchase a house together. It is important for you to find out what may contributing to this financial issue. Is he not working? Is he spending his money on things that are not necessities? Is he using drugs or alcohol? Are there expenses that need to be cut? Particularly if you are living together, you have a right to this information. It may be helpful for you both to talk together about any areas in which you may be able to cut costs to allow you to begin paying down the bills and reducing the stress level.
You may find the following link helpful in allowing you both to develop a budget that will help you to get your spending in control: http://financialplan.about.com/od/budgetingyourmoney/tp/budgeting-101.htm
You can also work on finding ways to have fun together without spending money, such as walks, picnics, turning on music and dancing, etc. Finding creative ways to have fun together will allow the stress of your situation to have less of an impact on your relationship.
I hope this answer is helpful. Please let me know if I can clarify further.