Hi there, I'm really sorry you are going through this. I know it is not easy, but I trust your heart knows for the best. Yes, I have been through a very similar situation. Last year, I had to end it with someone I was madly in love with, truly like no one I'd ever met before. However, we started to disconnect in what we want for our futures and I started having insane anxiety because I knew the end of us was coming, no matter how much I thought them to be the love of my life. What bothered me most was seeing them seemingly completely fine while I was losing my mind.
Leading up to our relationship's end, I ended up in the hospital--and I'd never been to a hospital before in my life. I had mysterious chest pains and my loved ones advised me to go to the ER. I was broken-hearted and experienced what I later learned to be my first anxiety attack. It was awful, and shocking (I'm normally a very calm, confident, and secure person. I really wasn't acting myself around this time, and my loved ones were concerned.). And then in the next month, I moved houses, but I couldn't even pack. I was overwhelmed easily and had more anxiety attacks.
The worst part at this point? We had broken up and went no-contact. The person who I relied on to relieve my anxiety was no longer within my reach. But you know what took me a really long time to realize? It was that the person who relieved my anxiety was also the person who brought it. I let myself take too long to accept that. You do not deserve anxiety. There are people out there who bring out the BEST in you, and clearly he does not today, so I applaud you for your bravery in this process. The BEST in you is happiness, peace, safety, and comfort--nothing close to anxiety! Believe me when I say you are not alone!
The more I enabled this person to have such a hold on my life, the more my anxiety would linger. I finally went to therapy (no meds for me either) and what I learned there helps me with myself and with all my relationships--and yes, it helped with anxiety.
My family members and friends were also the ones who helped me to open my eyes. They are probably right in claiming that your ex is the source of your anxiety. For me, the person who once brought out the best in me became the person who brought out the worst. That is a very sad realization and one that I still struggle to get over sometimes. You may be experiencing the same thing--again, you are not alone.
I learned that sometimes, it takes a few tries to leave someone before it finally happens. You will eventually learn that your heart has had enough and that you deserve better (I assume there are good reasons for this split, and don't ever forget those reasons). You will miss them. You felt safe to fall into depending on them, and you may have lost yourself in the process. That's okay.
Right now, just feel. Time will heal. Soon, surround yourself with others even if you can't stop thinking about him the whole time--just force yourself to stay busy. Definitely recommend therapy asap because I personally wish I went sooner. Time will heal. For the next time you have anxiety attacks, have a designated person you can call. For me it was my sister. She would tell me, "Sit down, put your back against the wall, breathe. Try to slow your breath. Calm your body, breathe." And drink water! Friends are your support systems for a reason. Eventually, you will be self-dependent again, I promise you. But right now it's okay to not be there yet. That's why I stress the involvement of others and sheer busyness greatly in your life right now. Time will heal.
If you choose not to have that designated person to call, Stranger, please remember my words there and tell them to yourself. You will be okay, you must remind yourself that you WILL be okay because greater things and people are in store for you. Trust the truth of this all happening for a reason, and you are so so so brave.
Lastly (sorry this is so long... I'm passionate!), yes, you will improve. Your heart will heal. Do not continue to enable because that will stop your heart from healing (don't leave chips out for the ants, my sister tells me). Begin by telling yourself that you do NOT need him to relieve anxiety. He gave it to you in the first place, I have no doubt. Meds, weed, and alcohol literally could have a similar relieving effect... but is that how you want to heal? Nope! Do you want to heal naturally as you've said? Yep! So, understand that natural healing begins with yourself. You are all you need, girlfriend. You are so strong!