Hi, I'd like to help you with your question.
It sounds like from what you said that you are under enormous stress. First you dealt with the stress of your mother's passing, then caring for your father, and now dealing with financial stress. All of these are major stressors.
You said you are on medication which tells me that you have at least seen your regular doctor if not a psychiatrist. But you did not say if you are seeing a therapist. I would highly recommend that you talk with someone. This will not only help you figure out exactly what you are feeling, but it would give you much needed support that you are not getting right now from your fiance. There are low cost or free resources available. Contact your local community mental health agency to see what they can offer you.
Although you have gone through and are still going through some very major stressors, there are options you can take to improve your situation. Besides talking with a therapist, if you have a church you attend, try talking with a pastor. They can offer support and may know of community resources you can try to help with your financial problems. Having your finace join you either in therapy or with the pastor can give him support as well and he can learn ways to help you cope.
The PTSD Workbook: Simple, Effective Techniques for Overcoming Traumatic Stress Symptoms by Mary Beth Williams and Soili Poijula is another resource you can try. It may give you a start in understanding what you are feeling and help you find some ways to feel better. You can find it either at Amazon.com or your local library may have a copy.
Hang in there. If you can seek out help, you will gain strength to help you feel better and life will get easier.
I hope this helped,