Struggling with Intrusive Thoughts and Faith

Assalamu alaikum. I'm a Muslim sister, and I've been dealing with OCD for as long as I can remember. It's touched every part of my life, but lately it's been messing with my deen. I keep getting stuck on thoughts about death and the akhirah, and it triggers these awful anxiety attacks. To cope, I started digging into Islam, and sometimes I'd feel at ease for a bit. But then the doubts would creep back in. It became like a ritual-I'd research Islam every single day just to avoid feeling like I'd fallen into kufr. But the doubts never fully left; they just kept returning. It's terrifying because even though I was learning and feeling convinced, the thoughts wouldn't stop. I began to fear that maybe I had committed kufr without realizing it. I kept reciting the shahada over and over, praying, doing dhikr, and making dua to Allah. I recently got married, but because the thoughts are still there, I'm scared my nikah might not be valid. At the time of my nikah, I was praying all five salah, praying tahajjud, reading Quran, and doing dhikr-but with all these doubts about Islam swirling in my head, is it possible that I left the fold of Islam? My question is: Has my nikah become invalid? Have I fallen into kufr? And how can I stop these thoughts from tormenting me?