For starters, you're not crazy
I have been diagnosed by a professional as having GAD and I can personally relate to 2 things in your post and all the other sound like GAD as well. Some GAD sufferers worry specifically about one type of thing more where some might just worry about everything in general. There is no clear cut script for this.
This stuck out to me personally: "I'm terrified of losing him though, of being alone again and in some weird way that makes me lash out at him, every time we fight i think this is it, the beginning of the end, lets just get it over with....even if it's over something silly like who ate the biscuits! Our sex life has ground to a halt, I', tense and nervous every time i even think about it"
My GAD completely revolves around my interpersonal relationships, specifically my romantic relationships. My doctor talks a lot about the "Glass Mountain". At the top of the mountain is happiness which is where we all want to be. At the bottom is loneliness, it's where we self-loathe about how life sucks and no one likes us and we're doomed to fail...no one likes being at the bottom of the mountain. As someone with GAD, as we climb the mountain to try to reach happiness, we continue to slip on 'banana peels', these peels represent our compulsions and repetitious, anxious behavior. We self-sabotage. As we get to happiness, we tell ourselves that we're not good enough, we will fail anyways so why bother, how could someone even like us, we aren't good enough, they will leave anyways...all these negative thoughts. And slowly but surely, we slide back down the mountain to the bottom where we are alone and unhappy again. But it's what we're used to, so that is what's 'normal' to us. It's when you're slipping on these banana peels that you have to try to retrain your brain away from these negative thoughts. We are prone to over analyze, and destroy. We are so self absorbed in our own thoughts about anxiety that we sabotage everything around us.
I too lash out in anger towards my partner. I must always feel like I am in full control. If not, it angers me. I am so consumed with trying to make sure nothing bad happens that I become so over bearing and over analyzing that I begin to live out the very thing I am trying to avoid. I almost look for things to be wrong, or I always assume he's doing something wrong because my mind is telling me that it's going to happen anyways. It's a vicious, exhausting cycle.
You should do some research about categorizing distorted thoughts for people with anxiety. These thoughts you have fit into specific categories and you may be prone to some more than others. What my doctor is trying to teach me to do is when I am in the anxious frame of mind, to categorize my thought, this makes me aware that the thought is distorted and I'm more able to rationalize myself away from it.
The most important things she has asked me are: I'm so focused on being in control, but have I ever had full control and do I know anyone that had 100% control of a situation? NO is the answer to both. We must learn to be ok with variables. Secondly, she asked me, have these anxious thoughts ever helped change the situation, did they make it better or did they help avoid something horrible? NO is the answer to all of those as well.
Worrying is ok and perfectly normal, but it won't fix or avoid anything that is going to happen anyways..there is a healthy amount of worry we should all have as human beings but we, as anxious people, need to figure out where that is.
I hope this helps a little and I'd be happy to pass on any other knowledge I have if it benefits you in any way!