Around people who know you quite well, like your family or your fiancé, you could try to simply write down what you want to communicate. Take a moment to think it over, put it down on a piece of paper, then give it to them to read. Many people on the spectrum can communicate more clearly when they write things down.
Another thing you could try is to work out a "colour code". Try to find colours that you associate with certain emotions or states of mind and make cards that show that colour. Then explain to the people close to you what the individual colours mean to you and maybe add a key word or two to each card so it will be easier for them to remember the meanings of each colour. When you run into difficulties expressing what is going on inside of you, you can then hold up the corresponding card to give them some quick information about how you are feeling or if a meltdown/panic attack/wrath outbreak might be impending. Instead of colours you could also use pictures that hold a similar significance for you, but I think it is easier for most people to work with colours as those don't trigger so many additional associations.
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Yes, I am serious about that avatar...