You have 4 anti-TNFs plus Cosentyx. If, in the worst case, like you said, each lasts only 2 years that gives 8 years on anti-TNFs. Plus another two on Cosentyx. Plus another two if you try both Simponi and Simponi Aria (IV version).
I have done ALL of this. Like you, I worried a lot about running out of options. When you start biologics at 15, your options diminish fairly quickly, especially since at the time, only Enbrel, Humira and Remicade were given to kids.
I can tell you honestly that my anxiety made everything worse. It made me hyperaware of every site of pain. It made me think I was flaring when I wasn't. It can cause muscle spasms. It can make minor pain into major pain. It caused many sleepless night. It has taken years of working with a therapist and now I'm better at bracketing that anxiety. The thing is, it's out of your control. You have no idea how long these drugs will last. But I can tell you this for sure - there are several more biologics in the works. I see Dr. Reveille in Texas, who is a big AS researcher. He always tells me what is the next option coming down the pipeline.
You have 10 years or so before you even have to worry about what is coming down the pipeline. And it could be much longer. There are people who last between 5-10 years on a single biologic.
Right now, you aren't even sure you're in a flare. Honestly, from reading your other threads, all of your symptoms sound muscular (shoulder blade pain for example is often from a muscle spasm in that area). Your inflammatory markers are perfect. If you are really worried, I would encourage you to see your rheumatologist and have her examine your joints and ask for an MRI of your spine.
And most definitely keep seeing a psychologist.
Anxious people can work on becoming less anxious. For me it has taken a lot of time and I'm not always good at it, but it's pointless to worry about stuff you can't control. And anyway, I can guarantee that in 10 years, there will be other options.
I have ZERO FDA approved options left now. Do I worry? YES!!! Do I let it take over my life? NO! I'm going to enjoy this biologic while it works, instead of focusing on the fact that it might fail one day and then I'll have nothing left. I have tried Enbrel, Humira, Remicade, Simponi, Remicade (higher dose), Simponi Aria, Humira (again), Cimzia and Cosentyx, all with different combinations of DMARDs. I'm 24 so I have a long time to go.