Your doctor has seen and felt them so there's probably not much we can add to that, so let's focus on the anxiety part. Do you have anxiety about things a lot? Is this the only thing you get anxious about? The question is, do you have a chronic anxiety problem that's getting in the way of your life? If you do, a therapist who specializes in anxiety treatment might be able to help and also teach you some relaxation exercises to help you with this. Again, can't help you the neck, don't even know if what you're feeling are actually your lymph nodes or something else and you have seen a doctor about it.
Lymph nodes are a normal part of our immune system. It's great your doctor saw you and was able to tell you that the two lumps are not concerns and yet you are still very worried. That's hard. How much does this impact you? Are you constantly checking, not able to relax? Or worse? I think beginning to work on the anxiety would be a good idea. Some of that you can do at home by yourself. This includes improving your lifestyle if you need to. Daily exercise is very good for anxiety and mental health as a whole, eating well and getting proper rest. Listening to meditation apps like Calm or Headspace, practicing breathing exercises, heck, doing some yoga from a youtube video. :>) All is beneficial and helps sooth anxiety. If it is still at a high level and impacts your daily function, it is time to look into health anxiety. https://www.health.harvard.edu/mind-and-mood/always-worried-about-your-health-you-may-be-dealing-with-health-anxiety-disorder I start with my primary care doctor for help and referrals and this is a good place to start. Therapists can be very beneficial but ask questions before you see them to find one that you gel with. I try to work with my insurance to save money, I must admit. So, that may dictate some of your choices.