You are doing far too much of the heavy lifting. You can’t solve your boyfriend’s anxiety problems. It’s unfair of him to expect you to. In a way, he is asking you to be an amateur therapist because he isn’t willing to see a professional one.
Please stop trying so hard to do the impossible. You’ve done what you can to understand and to be supportive. No one else will be the “right” person for him if he has the idea that the right relationship will make the anxiety go away. No relationship will solve the problem. Only he can.
It is up to him. Cognitive-behavioral therapy is the treatment of choice for anxiety and OCD. In addition, there are medications that can help calm down the obsessive thinking. If he would engage in therapy for three to six months, and I mean really work at it, he likely would get considerable relief.
Please resign from your job as researcher and fixer. Instead, tell your boyfriend that you love him so much you don’t want him to have a rank beginner for a therapist. Instead, you are willing to be there for him as he finds a real therapist and begins the work to take charge of himself and his feelings.
I wish you well.