How to write a letter to fiance

Been together for over 4 years. Engaged for 2. I'm ill and been dependent on him the last 10 months, but Ive made him thousands of dollars recently by investing and selling his home. I do things around the house to help out, but have file for SSi and awaiting a hearing. We live together and he is well off due to my creative investments. But now that I have no money he gives me 20 here or there. I'm in food stamps and that helps. I just feel if we are going to spend our life together my struggles financially should be the least of my worries. He goes on many trips with his friends, but not me. I'm able to go away a few days at a time with my illness. I've been trying to be affectionate, but get turned away. I feel alone. I feel like saying get off the pot and marry me already. But he doesn't even bring it up. Not to be conceded but I'm a beautiful devoted woman and trust him 100%. He's not very good at communicating and I want to write him a letter to let him know I'm not a doormat and he needs to commit or I'm gone. I think he thinks I need him financially, which I do, but I feel he's taking my kindness for weakness. I'm lonely and tired of waiting. He's on a trip now and I want to write him while he's gone so when he comes home we can resolve this.