he barely touched me all night. I mentioned this and he got defensive and stormed out
I mentioned I might have to pay a visit to GP. He asked me if I'd ever been on meds before - this upset me
I mostly feel anxious in our relationship
Stop questioning the 'why's. All of the reasons behind these things are this: He is being who he is, and you are being who you are.
The only thing wrong with you is that you think there's something wrong with you. You can't change or control the way you feel. Nobody can, otherwise everybody would choose who to fall in love with, and we'd all choose to dislike chocolate and love treadmills. All you can do it choose how to respond.
So, you can opt for staying, and trying to change something unchangeable, which will lead you down a never ending spiral of cock-up, fueling your low self esteem to rocket power, or, you can opt for distance between you and anybody that makes you feel this way.
One of the big lessons is that feelings aren't inconveniences to be overcome. They are your heart, your core. They are the truest manifestation of the real, pure you that there is. Pushing aside this core part of you, rejecting it, minimising it, is the basis of your low self esteem, your relationship anxiety, and what you're calling your self sabotage.
I would call your 'self sabotage' 'boundaries'. It's when the real you bursts out uncontrollably and screams 'Get away from me, you're not right for me, I don't like how you make me feel!' or, if she's not doing that, she's sitting feeling depressed in a corner, saying 'What's the point? Nobody ever listens to me...'.
Your feelings are 100% right for you. Your sensitivities are 100% right for you. You can't get these things 'wrong'. There's no objective level of how much you should feel x or feel y. Anybody who loves you will respect your feelings, even if (or especially if) they are a bit more on the sensitive side. You won't feel anxious around the right people. Pretty much the only thing that makes the right people right is that you can be your true self around them and feel good about it. Everything else is peripheral.
Choose your people wisely, and you will find that you will have a much lower level of anxiety in your life. Choose your people by trying to change who you are in order to fit in, and you will feel constantly oppressed, depressed, and anxious.