Hey Jessica!
I'm so sorry to read about how you are feeling and how you are affected. Your story actually sounds extremely similar to mine, the only thing that I have never had is the back pain and slipped disks.
Whilst we aren't able to give medical advice, I can tell you that I have heard of these things being relate to PsA, and that I personally do experience a lot of them myself. I should say that I do have other diagnoses though. We have a number of articles which I think you may find interesting:
Fatigue: https://psoriatic-arthritis.com/psa-symptoms/fatigue/
Joint pain: https://psoriatic-arthritis.com/psa-symptoms/joint-pain-swollen-stiff/
Flaring and remission: https://psoriatic-arthritis.com/psa-basics/flare/
Tendons and ligaments: https://psoriatic-arthritis.com/psa-symptoms/tendons-ligaments/
Lower back pain: https://psoriatic-arthritis.com/psa-symptoms/lower-back-pain/
I think if after reading these they do all sound familiar, it is probably worth checking in with a doctor again and just asking for a clear explanation of what they think is going on. Often I don't think we are given enough information at diagnosis, especially if it is tentative like you say, and we are expected to just work things out for ourselves. When really doctors should be providing us with support and information!!
I hope this has been helpful. If you have any more questions, or would like to know about anything else, don't hesitate to ask! And please know that we are here for you anytime you need to chat or vent about anything. It can be really tough living with a chronic illness and we want to support you! 😀
Best,
CathyD