Hi Lbrooksie123,
My husband and I have tried 7 mattresses since January 2022. He is 5’9", 225 lbs, and I am 5’1", 105 lbs. We are both pretty physically fit, especially for our ages (57 and 55). My husband has no issues sleeping on anything. I am primarily a side or back sleeper. I am the problem apparently. Did not have any back pain at all prior to getting a new bed. I have have lower and middle back issues, and hip pain since trying these new mattresses. Also shoulder pain if I am on a too firm mattress.
Thank you for providing you and your husbands specifications, and for sharing your 7 different mattress experiences! I don’t imagine that was an easy task and my hat goes off to you for maintaining your sanity! I hope that discovering this forum will help you to find the solution you are looking for!
Tempurpedic Pro-Breeze Hybrid medium - hard as a rock and cold
Beautyrest Jennings Ultra Plush - marshmallow (this is where the back pain started)
Serta iSeries 3000 medium hybrid - defective. Mattresses slanted down from right to left if you looked at it head on from foot of bed. No lower back support.
Stearns and Foster Cassat Plush - I felt no support in my hips and mid back after sleeping on this for several weeks. Felt like my back was in ‘C’ shape if on back or side.
Tempurpedic Pro-Adapt medium all foam - too hard
Aireloom Preferred Streamline Luxury Firm - Could actually sleep on this one, however it was a bit hard for me at first. After wearing it in for 2 months, lower back pain started and some shoulder pain.
Aireloom Preferred Streamline Plush M1 - This bed was great for a month. Still had some small bit of lower back discomfort. After a month lower back pain set in again. Have resorted to various things like putting a folded towel under my hips. Some nights this helps, some not. Still struggling.
Many of the mattresses you’ve tried were either memory foam, or spring. Have you tried latex before? There is a lot of information on this forum about latex and its superior support. Many of the options can be customized on the left and right side of the mattress so that you and your husband don’t have to have the same firmness. Given your differences, I think this would benefit you both. Plus, none of the layers are glued together so that you can rearrange, swap or flip while you figure out which configuration best suites your sleep style. Depending on your location, there are many experts here that can help!
Anyone have suggestions for a PETITE sleeper???
As you’ve experienced and maybe read about on this forum, finding the perfect balance of firmness and softness can be a challenge for many!
When speaking directly towards mattresses, hip and shoulder pain or pressure can be an indication that it’s too firm and consistent lower or middle back pain can indication it’s too soft. Age, size, body shape, sleep position, posture, preference…and of course so many other aspects can directly impact our bodies and especially our sleep. I wish there was a simple recommendation that I had for petite sleepers, but I think the best thing to do would be to visit a local mattress store that has a selection of latex options, along with the normal memory/spring so that you can do a proper comparison.
I would love to share some other tips for side sleepers: 
Incorporating a body pillow between your legs when laying on your side is a great way to support your hips and shoulders. You can either use two Queen sizes, one to hug and one between your knees/ankles, or a King size might reach! And when laying on your back, you can incorporate it under your knees to relieve pressure from your lower back.
Also, how is the platform bed or the mattress support holding up. We see this far too often, beds that are manufactured with flexible slats that sag below flat creating a hammock. Or slats that are widely spread that pose a similar concern. The most ideal surface to support a mattress is something solid, with a center support for extra stability. To test it: look under the bed when someone is laying down or press down using your hands and see if there is movement.
I hope these comments and suggestions can help you get closer to your dream sleep!