Welcome to the forum!
Many of us here have back problems, so we sympathize with you! That being said, we also see many new members coming here looking for somewhat of a diagnoses. Our very best advice to give you, is to seek a professional medical opinion, as we simply are not Dr's, and can only share our experiences. We will also support you as needed.
I myself had a double lumbar fusion back in 2010, and now suffer from FBS (failed back syndrome)…and sleep most of the time on my back, with two pillows under my knees. I do try to sleep on my side from time to time, and I find that a pillow or two tucked between the knees will provide some comfort, as it helps align the hips to the spine correctly. I also find such as you that sleeping on my side is not the best source of comfort for me, and I pay for it the next day.
Again!…I would advise you to seek out a DR first to see what is causing your pain. Generally they may want to take X-rays and or an MRI, and if indeed they find a problem with the spine, they might start with PT (physical Therapy)…and if that does not provide relief, then injections of some sort might be tried, such as an Epidural. If all of that fails, then you may have a couple of options left, one being pain med's, and or corrective surgery.
Please let us know what your Dr finds out if you do indeed follow up with one.
The "Chronic Pain 101" located at the top of the forum page might be of interest to you, as there are some great articles there. I would also advise starting a pain journal, and you can find the format located within the "Chronic Pain 101" post.
Feel free to print it out, and start your journal. It may help give your Dr a better picture of just how much you are suffering….so please do take it to your Dr appointment with you.
Again Welcome!..and Enjoy the forum!
Moderator Chronic Pain Forum
Weekly Quote! "Getting over a painful experience is much like crossing monkey bars. You have to let go at some point in order to move forward."