I can relate to this, your anxiety making you needing reassurance, which isn't always forthcoming in the way you wish it to be, then the ensuing stress it causes between you and your partner. What you've written reminds me of the years of anxiety I suffered. But how to stop this..
Well, for me there was no instant cure. I didn't take tablets, instead I had to force myself to think of something else, distract myself from how I was feeling. Be kind to yourself, make a list of things you're grateful for and concentrate on those things, remember a happy event, talk to yourself in a reassuring way (this one was very important for me - talking myself up), anything to stop the cycle of anxiety.
The anxious thoughts will keep coming back, so turn them around and think of something positive. It helps if you write the positive/distracting things down, so when you're in the middle of an anxious episode you can see the coping strategies written down, instead of desperately trying to think of them while your mind is wracked with anxiety.
Then do something nice. Listen to music, get some colouring pencils and one of those adult colouring in books. Go for a walk. These were head clearing strategies which worked for me, eventually. It took months of hard work.
I think (maybe from your partner's point of view) unless you've suffered with anxiety it is very hard to fully understand someone who does.
You could always go back on the tablets you took previously, as you say, you're not adverse to doing that.